path: root/docs/libxml.dbk

<?xml version="1.0" encoding="UTF-8"?>
<!-- -*- nxml -*- -->
<book lang="en-us">
    <title>XML::LibXML</title>

    <bookinfo>
        <authorgroup>
            <author>
                <firstname>Matt</firstname>
                <surname>Sergeant</surname>
            </author>

            <author>
                <firstname>Christian</firstname>
                <surname>Glahn</surname>
            </author>

            <author>
                <firstname>Petr</firstname>
                <surname>Pajas</surname>
            </author>
        </authorgroup>


        <edition>2.0200</edition>
        <copyright>
            <year>2001-2007</year>
            <holder>AxKit.com Ltd</holder>
        </copyright>
	<copyright>
	  <year>2002-2006</year>
	  <holder>Christian Glahn</holder>
	</copyright>
	<copyright>
	  <year>2006-2009</year>
	  <holder>Petr Pajas</holder>
	</copyright>
    </bookinfo>

    <chapter id="README">
        <title>Introduction</title>

        <titleabbrev>README</titleabbrev>

        <para>This module implements a Perl interface to the Gnome
          libxml2 library which provides
          interfaces for parsing and manipulating XML files. This
          module allows Perl programmers to make use of the highly
          capable validating XML parser and the high performance DOM
          implementation.</para>

        <sect1>
            <title>Important Notes</title>

            <para>XML::LibXML was almost entirely reimplemented between version 1.40 to version 1.49. This may cause problems on some production machines. With
            version 1.50 a lot of compatibility fixes were applied, so programs written for XML::LibXML 1.40 or less should run with version 1.50 again.</para>
            <para>In 1.59, a new callback API was introduced. This new API is not compatible with the previous one.
	       See XML::LibXML::InputCallback manual page for details.</para>
 	    <para>In 1.61 the XML::LibXML::XPathContext module, previously distributed separately, was merged in.</para>
	    <para>An experimental support for Perl threads introduced in 1.66 has been replaced in 1.67.</para>
        </sect1>

        <sect1>
            <title>Dependencies</title>

            <para>Prior to installation you MUST have installed the libxml2 library. You can get the latest libxml2 version from</para>

            <para>http://xmlsoft.org/</para>

            <para>Without libxml2 installed this module will neither build nor run.</para>

            <para>Also XML::LibXML requires the following packages:</para>

            <itemizedlist>
                <listitem>
                    <para>XML::SAX - base class for SAX parsers</para>
                </listitem>

                <listitem>
                    <para>XML::NamespaceSupport - namespace support for SAX parsers</para>
                </listitem>

            </itemizedlist>

            <para>These packages are required. If one is missing some tests will fail.</para>

            <para>Again, libxml2 is required to make XML::LibXML work. The library is not just required to build XML::LibXML, it has to be accessible during
            run-time as well. Because of this you need to make sure libxml2 is installed properly. To test this, run the xmllint program on your system. xmllint
            is shipped with libxml2 and therefore should be available.
            For building the module you will also need the header file for libxml2, which in binary
            (.rpm,.deb) etc. distributions usually dwell in a package named libxml2-devel or similar.</para>
        </sect1>

        <sect1>
            <title>Installation</title>
	    <para>(These instructions are for UNIX and GNU/Linux systems. For MSWin32,
See Notes for Microsoft Windows below.)</para>
            <para>To install XML::LibXML just follow the standard installation routine for Perl modules:</para>

            <orderedlist>
                <listitem>
                    <para>perl Makefile.PL</para>
                </listitem>

                <listitem>
                    <para>make</para>
                </listitem>

                <listitem>
                    <para>make test</para>
                </listitem>

                <listitem>
                    <para>make install # as superuser</para>
                </listitem>
            </orderedlist>

            <para>Note that XML::LibXML is an XS based Perl extension and you need a C compiler
              to build it.</para>
            <para>Note also that you should rebuild XML::LibXML if you upgrade libxml2
                  in order to avoid problems with possible binary incompatibilities between releases of the library.</para>

            <sect2>
                <title>Notes on libxml2 versions</title>

                <para>XML::LibXML requires at least
                  libxml2 2.6.16 to compile and pass all tests and
	          at least 2.6.21 is required for XML::LibXML::Reader.
                  For some older OS versions this means that an
                  update of the pre-built packages is required.</para>

                <para>Although libxml2 claims binary compatibility between
		its patch levels, it is a good idea to recompile XML::LibXML
		and run its tests after an upgrade of libxml2.
	        </para>

	<para>If your libxml2 installation is not within your $PATH,
	  you can pass the XMLPREFIX=$YOURLIBXMLPREFIX parameter to Makefile.PL
	  determining the correct libxml2 version in use. e.g.
	</para>

                <programlisting> perl Makefile.PL XMLPREFIX=/usr/brand-new </programlisting>

                <para>will ask '/usr/brand-new/bin/xml2-config' about your real libxml2 configuration.</para>

                <para>Try to avoid setting INC and LIBS directly on the
                command-line, for if used, Makefile.PL does not check
                the libxml2 version for compatibility with XML::LibXML.</para>
            </sect2>

            <sect2>
                <title>Which version of libxml2 should be used?</title>

                <para>XML::LibXML is tested against a couple versions of
                libxml2 before it is released. Thus there are versions
                of libxml2 that are known not to work properly with
                XML::LibXML. The Makefile.PL keeps a blacklist of
                the incompatible libxml2 versions.</para>

                <para>If Makefile.PL detects one of the incompatible versions,
                it notifies the user. It may still happen that
                XML::LibXML builds and pass its tests with such
                a version, but that does not mean everything
                is OK. There will be no support at all for blacklisted versions!</para>

                <para>As of XML::LibXML 1.61, only versions 2.6.16 and higher are supported.
                   XML::LibXML will probably not compile with earlier libxml2 versions than
                   2.5.6. Versions prior to 2.6.8 are known to be broken for various reasons,
                   versions prior to 2.1.16 exhibit problems with namespaced attributes
                   and do not therefore pass XML::LibXML regression tests.
                </para>

                <para>It may happen that an unsupported version of libxml2
                passes all tests under certain conditions. This is no
                reason to assume that it shall work without problems.
                If Makefile.PL marks a version of libxml2 as incompatible or broken
                it is done for a good reason.</para>
            </sect2>

            <sect2>
                <title>Notes for Microsoft Windows</title>

                <para>Thanks to Randy Kobes there is a pre-compiled PPM package available on</para>
                <para>http://theoryx5.uwinnipeg.ca/ppmpackages/</para>

                <para>Usually it takes a little time to build the package for the latest release.</para>
		<para>If you want to build XML::LibXML on Windows from source, you can use
		the following instructions contributed by Christopher J. Madsen:</para>

		<para>These instructions assume that you already have your system set up to
		compile modules that use C components.
		</para>
		<para>
		First, get the libxml2 binaries from http://xmlsoft.org/sources/win32/
		(currently also available at http://www.zlatkovic.com/pub/libxml/).
		</para>
		<para>
		  You need:
		</para>
		<programlisting>  iconv-VERSION.win32.zip
  libxml2-VERSION.win32.zip
  zlib-VERSION.win32.zip</programlisting>
  <para>Download the latest version of each. (Each package will probably have
  a different version.) When you extract them, you'll get directories
  named iconv-VERSION.win32, libxml2-VERSION.win32, and
  zlib-VERSION.win32, each containing bin, lib, and include directories.</para>
  <para>Combine all the bin, include, and lib directories under c:\Prog\LibXML.
  (You can use any directory you prefer; just adjust the instructions
  accordingly.)</para>
  <para>Get the latest version of XML-LibXML from CPAN.
  Extract it.</para>
  <para>Issue these commands in the XML-LibXML-VERSION directory:</para>
  <programlisting>  perl Makefile.PL INC=-Ic:\Prog\LibXML\include LIBS=-Lc:\Prog\LibXML\lib
  nmake
  copy c:\Prog\LibXML\bin\*.dll blib\arch\auto\XML\LibXML
  nmake test
  nmake install</programlisting>
  <para>(Note: Some systems use dmake instead of nmake.)</para>
  <para>By copying the libxml2 DLLs to the arch directory, you help avoid
  conflicts with other programs you may have installed that use other
  (possibly incompatible) versions of those DLLs.</para>
	    </sect2>
            <sect2>
                <title>Notes for Mac OS X</title>

                <para>Due refactoring the module, XML::LibXML will not
                run with some earlier versions of Mac OS X. It appears that this is related
                to special linker options for that OS prior to version
                10.2.2. Since the developers do not have full access to this OS,
                help/ patches from OS X gurus are highly
                appreciated.</para>

                <para>It is confirmed that XML::LibXML builds and runs
                without problems since Mac OS X 10.2.6.</para>
            </sect2>

            <sect2>
                <title>Notes for HPUX</title>

                <para>XML::LibXML requires libxml2 2.6.16 or
                later. There may not exist a usable binary
                libxml2 package for HPUX and XML::LibXML. If
                HPUX cc does not compile libxml2
                correctly, you will be forced to recompile perl with
                gcc (unless you have already done that).</para>

                <para>Additionally I received the following Note from Rozi Kovesdi:</para>

                <programlisting>Here is my report if someone else runs into the same problem:

Finally I am done with installing all the libraries and XML Perl
modules

The combination that worked best for me was:
gcc
GNU make

Most importantly - before trying to install Perl modules that depend on
libxml2:

must set SHLIB_PATH  to include  the path to  libxml2 shared library

assuming that you used the default:

export  SHLIB=/usr/local/lib

also, make sure that the config  files have execute permission:

/usr/local/bin/xml2-config
/usr/local/bin/xslt-config

they did not have +x after they were installed by 'make install'
and it took me a while to realize that this was my problem

or one can use:

perl Makefile.PL LIBS='-L/path/to/lib' INC='-I/path/to/include'</programlisting>
            </sect2>
        </sect1>

        <sect1>
            <title>Contact</title>

            <para>For bug reports, please use the CPAN request tracker on http://rt.cpan.org/NoAuth/Bugs.html?Dist=XML-LibXML</para>

            <para>For suggestions etc. you may contact the maintainer directly at "pajas at ufal dot mff dot cuni dot cz", but in general, it is recommended to use the mailing list given below.
            </para>

            <para>For suggestions etc., and other issues
	    related to XML::LibXML you may use the perl XML mailing list
            (<email>perl-xml@listserv.ActiveState.com</email>),
	    where most XML-related Perl modules are discussed.
	    In case of problems you should check the archives of that
            list first. Many problems are already discussed there. You
            can find the list's archives and subscription options at
	    http://aspn.activestate.com/ASPN/Mail/Browse/Threaded/perl-xml</para>
        </sect1>

        <sect1>
            <title>Package History</title>

            <para>Version &lt; 0.98 were maintained by Matt Sergeant</para>

            <para>0.98 &gt; Version &gt; 1.49 were maintained by Matt Sergeant and Christian Glahn</para>

            <para>Versions &gt;= 1.49 are maintained by Christian Glahn</para>

            <para>Versions &gt; 1.56 are co-maintained by Petr Pajas</para>

            <para>Versions &gt;= 1.59 are provisionally maintained by Petr Pajas</para>
        </sect1>

        <sect1>
            <title>Patches and Developer Version</title>

            <para>As XML::LibXML is open source software, help and
            patches are appreciated. If you find a bug in the current
            release, make sure this bug still exists in the developer
            version of XML::LibXML. This version can be cloned
            from its Git repository. For more information about that,
            see:</para>

            <para>https://github.com/shlomif/perl-XML-LibXML</para>

            <para>Please consider all regression tests as correct. If
            any test fails it is most certainly related to a
            bug.</para>

            <para>If you find documentation bugs, please fix them in
            the libxml.dbk file, stored in the docs directory.</para>
        </sect1>

        <sect1>
            <title>Known Issues</title>

            <para>The push-parser implementation causes memory leaks.</para>
        </sect1>
    </chapter>

    <chapter id="LICENSE">
        <title>License</title>

        <titleabbrev>LICENSE</titleabbrev>

        <para>This is free software, you may use it and distribute it under the same terms as Perl itself.</para>

        <para>Copyright 2001-2003 AxKit.com Ltd., 2002-2006 Christian Glahn, 2006-2009 Petr Pajas</para>

        <sect1>
            <title>Disclaimer</title>

            <para>THIS PROGRAM IS DISTRIBUTED IN THE HOPE THAT IT WILL
            BE USEFUL, BUT WITHOUT ANY WARRANTY; WITHOUT EVEN THE
            IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A
            PARTICULAR PURPOSE.</para>
        </sect1>
    </chapter>

    <chapter id="XML-LibXML">
        <title>Perl Binding for libxml2</title>

        <titleabbrev>XML::LibXML</titleabbrev>

        <sect1>
            <title>Synopsis</title>

            <programlisting>use XML::LibXML;
my $dom = XML::LibXML-&gt;load_xml(string => &lt;&lt;'EOT');
&lt;some-xml/&gt;
EOT</programlisting>
        </sect1>

        <sect1>
            <title>Description</title>

            <para>This module is an interface to libxml2, providing
	    XML and HTML parsers with DOM, SAX and XMLReader interfaces,
	    a large subset of DOM Layer 3 interface and
	    a  XML::XPath-like interface to XPath API of libxml2.
	    The module is split into several packages which are not described in this section;
	    unless stated otherwise, you only need to <literal>use XML::LibXML;</literal>
	    in your programs.</para>

            <para>For further information, please check the following documentation:</para>

            <variablelist>
                <varlistentry>
                    <term><xref linkend="XML-LibXML-Parser"/></term>

                    <listitem>
                        <para>Parsing XML files with XML::LibXML</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-DOM"/></term>

                    <listitem>
                        <para>XML::LibXML Document Object Model (DOM) Implementation</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-SAX"/></term>

                    <listitem>
                        <para>XML::LibXML direct SAX parser</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-Reader"/></term>

                    <listitem>
                        <para>Reading XML with a pull-parser</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-Dtd"/></term>

                    <listitem>
                        <para>XML::LibXML frontend for DTD validation</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-RelaxNG"/></term>

                    <listitem>
                        <para>XML::LibXML frontend for RelaxNG schema validation</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-Schema"/></term>

                    <listitem>
                        <para>XML::LibXML frontend for W3C Schema schema validation</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-XPathContext"/></term>
                    <listitem>
                        <para>API for evaluating XPath expressions with enhanced support
			for the evaluation context</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-InputCallback"/></term>

                    <listitem>
                        <para>Implementing custom URI Resolver and input callbacks</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-Common"/></term>
                    <listitem>
                        <para>Common functions for XML::LibXML related Classes</para>
                    </listitem>
                </varlistentry>
	    </variablelist>
            <para>The nodes in the Document Object Model (DOM) are represented by the following classes
	    (most of which "inherit" from <xref linkend="XML-LibXML-Node"/>):</para>
	    <variablelist>
                <varlistentry>
                    <term><xref linkend="XML-LibXML-Document"/></term>

                    <listitem>
                        <para>XML::LibXML class for DOM document nodes</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-Node"/></term>

                    <listitem>
                        <para>Abstract base class for XML::LibXML DOM nodes</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-Element"/></term>

                    <listitem>
                        <para>XML::LibXML class for DOM element nodes</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-Text"/></term>

                    <listitem>
                        <para>XML::LibXML class for DOM text nodes</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-Comment"/></term>

                    <listitem>
                        <para>XML::LibXML class for comment DOM nodes</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-CDATASection"/></term>

                    <listitem>
                        <para>XML::LibXML class for DOM CDATA sections</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-Attr"/></term>

                    <listitem>
                        <para>XML::LibXML DOM attribute class</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-DocumentFragment"/></term>

                    <listitem>
                        <para>XML::LibXML's DOM L2 Document Fragment implementation</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-Namespace"/></term>

                    <listitem>
                        <para>XML::LibXML DOM namespace nodes</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><xref linkend="XML-LibXML-PI"/></term>

                    <listitem>
                        <para>XML::LibXML DOM processing instruction nodes</para>
                    </listitem>
                </varlistentry>

            </variablelist>
        </sect1>
	<sect1>
            <title>Encodings support in XML::LibXML</title>
            <para>Recall that since version 5.6.1, Perl distinguishes between
            character strings (internally encoded in UTF-8) and so
            called binary data and, accordingly, applies either
            character or byte semantics to them.  A scalar
            representing a character string is distinguished from
	    a byte string by special flag (UTF8). Please refer to <emphasis>perlunicode</emphasis> for details.
	    </para>
	    <para>
	      XML::LibXML's API is designed to deal with many
	      encodings of XML documents completely transparently, so
	      that the application using XML::LibXML can be completely
	      ignorant about the encoding of the XML documents it works with.
	      On the other hand, functions like <function>XML::LibXML::Document-&gt;setEncoding</function>
	      give the user control over the document encoding.
	    </para>
	    <para>
	      To ensure the aforementioned transparency and
	      uniformity, most functions of XML::LibXML that work with
	      in-memory trees accept and return data as character
	      strings (i.e. UTF-8 encoded with the UTF8 flag on)
	      regardless of the original document encoding; however,
	      the functions related to I/O operations (i.e. parsing
	      and saving) operate with binary data (in the original
	      document encoding) obeying the encoding declaration of
	      the XML documents.</para>
	    <para>Below we summarize basic rules and principles
	    regarding encoding:
	    </para>
	    <orderedlist>
	      <listitem><para>Do NOT apply any encoding-related PerlIO layers
	      (<literal>:utf8</literal> or <literal>:encoding(...)</literal>)
	      to file handles that are an input for the parses
	      or an output for a serializer of (full) XML documents.
	      This is because the conversion of the data to/from the internal character representation
	      is provided by libxml2 itself which must be able to enforce the encoding
	      specified by the <literal>&lt;?xml version="1.0" encoding="..."?&gt;</literal>
	      declaration. Here is an example to follow:
	      <programlisting>use XML::LibXML;
# load
open my $fh, '&lt;', 'file.xml';
binmode $fh; # drop all PerlIO layers possibly created by a <literal>use open</literal> pragma
$doc = XML::LibXML-&gt;load_xml(IO => $fh);

# save
open my $out, '&gt;', 'out.xml';
binmode $out; # as above
$doc-&gt;toFH($out);
# or
print {$out} $doc-&gt;toString();</programlisting>
	      </para>
	      </listitem>
	      <listitem>
		<para>All functions working with DOM accept and return
		character strings (UTF-8 encoded with UTF8 flag on). E.g.
		<programlisting><![CDATA[
my $doc = XML::LibXML::Document->new('1.0',$some_encoding);
my $element = $doc->createElement($name);
$element->appendText($text);
$xml_fragment = $element->toString(); # returns a character string
$xml_document = $doc->toString(); # returns a byte string
]]>
		</programlisting>
		where
		<literal>$some_encoding</literal> is the document encoding
		that will be used when saving the document,
		and <literal>$name</literal> and <literal>$text</literal>
		contain character strings (UTF-8 encoded with UTF8 flag on).
		Note that the method <function>toString</function>
		returns XML as a character string if applied to
		other node than the Document node and
		a byte string containing the appropriate
		<programlisting>&lt;?xml version="1.0" encoding="..."?&gt;</programlisting>
		declaration if applied to a <xref linkend="XML-LibXML-Document"/>.
		</para>
	      </listitem>
	      <listitem>
		<para>DOM methods also accept binary strings in the original encoding of the
		document to which the node belongs (UTF-8 is assumed if the node is not
		attached to any document). Exploiting this feature is NOT RECOMMENDED
		since it is considered bad practice.
		</para>
		<programlisting><![CDATA[
my $doc = XML::LibXML::Document->new('1.0','iso-8859-2');
my $text = $doc->createTextNode($some_latin2_encoded_byte_string);
# WORKS, BUT NOT RECOMMENDED!
]]>
		</programlisting>
	      </listitem>
	    </orderedlist>
            <para><emphasis>NOTE:</emphasis> libxml2 support for many
            encodings is based on the iconv library.  The actual list
            of supported encodings may vary from platform to
            platform. To test if your platform works correctly with
            your language encoding, build a simple document in the
            particular encoding and try to parse it with XML::LibXML
            to see if the parser produces any errors. Occasional
            crashes were reported on rare platforms that ship with a broken
            version of iconv.</para>
	</sect1>
        <sect1>
	  <title>Thread Support</title>
	  <para>
	    XML::LibXML since 1.67 partially supports Perl threads
	    in Perl >= 5.8.8. XML::LibXML can be used with threads
	    in two ways:
	  </para>
	  <para>
	    By default, all
	    XML::LibXML classes use CLONE_SKIP class method
	    to prevent Perl from copying XML::LibXML::* objects
	    when a new thread is spawn.
	    In this mode, all XML::LibXML::* objects are thread specific.
	    This is the safest way
	    to work with XML::LibXML in threads.
	  </para>
	  <para>
	    Alternatively, one may use
	  </para>
	  <programlisting>use threads;
use XML::LibXML qw(:threads_shared);</programlisting>
	  <para>
	    to indicate, that
	    all XML::LibXML node and parser objects
	    should be shared between the main thread
	    and any thread spawn from there.
	    For example, in
	  </para>
	  <programlisting>my $doc = XML::LibXML->load_xml(location => $filename);
my $thr = threads->new(sub{
  # code working with $doc
  1;
});
$thr->join;
</programlisting>
         <para>
	   the variable <literal>$doc</literal>
	   refers to the exact same XML::LibXML::Document
	   in the spawned thread as in the main thread.
	 </para>
	 <para>
	   Without using mutex locks,
	   parallel threads may read the same document
	   (i.e. any node that belongs to the document),
	   parse files, and modify different documents.
	 </para>
	 <para>
	   However, if there is a chance that
	   some of the threads will attempt to modify a document
	   (or even create
	   new nodes based on that document,
	   e.g. with <literal>$doc->createElement</literal>)
	   that other threads may be reading at the same time,
	   the user is responsible for creating a mutex lock
	   and using it in <emphasis>both</emphasis>
	   in the thread that modifies and
	   the thread that reads:
	 </para>
	  <programlisting>my $doc = XML::LibXML->load_xml(location => $filename);
my $mutex : shared;
my $thr = threads->new(sub{
   lock $mutex;
   my $el = $doc->createElement('foo');
   # ...
  1;
});
{
  lock $mutex;
  my $root = $doc->documentElement;
  say $root->name;
}
$thr->join;
</programlisting>
<para>Note that libxml2 uses dictionaries to store short strings and
these dictionaries are kept on a document node. Without mutex locks, it
could happen in the previous example that the thread modifies the
dictionary while other threads attempt to read from it, which could
easily lead to a crash.</para>
	</sect1>
        <sect1>
            <title>Version Information</title>

            <para>Sometimes it is useful to figure out, for which
            version XML::LibXML was compiled for. In most cases this
            is for debugging or to check if a given installation meets
            all functionality for the package. The functions
            XML::LibXML::LIBXML_DOTTED_VERSION and
            XML::LibXML::LIBXML_VERSION provide this version
            information. Both functions simply pass through the values
            of the similar named macros of libxml2.
	    Similarly, XML::LibXML::LIBXML_RUNTIME_VERSION returns
            the version of the (usually dynamically) linked libxml2.
            </para>

            <variablelist>
                <varlistentry>
                    <term>XML::LibXML::LIBXML_DOTTED_VERSION</term>

                    <listitem>
                        <funcsynopsis>
                            <funcsynopsisinfo>$Version_String = XML::LibXML::LIBXML_DOTTED_VERSION;</funcsynopsisinfo>
                        </funcsynopsis>

                        <para>Returns the version string of the
                        libxml2 version XML::LibXML was compiled
                        for. This will be "2.6.2" for "libxml2
                        2.6.2".</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term>XML::LibXML::LIBXML_VERSION</term>

                    <listitem>
                        <funcsynopsis>
                            <funcsynopsisinfo>$Version_ID = XML::LibXML::LIBXML_VERSION;</funcsynopsisinfo>
                        </funcsynopsis>

                        <para>Returns the version id of the libxml2
                        version XML::LibXML was compiled for. This
                        will be "20602" for "libxml2 2.6.2". Don't mix
                        this version id with
                        $XML::LibXML::VERSION. The latter contains the
                        version of XML::LibXML itself while the first
                        contains the version of libxml2 XML::LibXML
                        was compiled for.</para>
                    </listitem>
                </varlistentry>
                <varlistentry>
                    <term>XML::LibXML::LIBXML_RUNTIME_VERSION</term>

                    <listitem>
                        <funcsynopsis>
                            <funcsynopsisinfo>$DLL_Version = XML::LibXML::LIBXML_RUNTIME_VERSION;</funcsynopsisinfo>
                        </funcsynopsis>

                        <para>Returns a version string of the libxml2
                        which is (usually dynamically) linked by
                        XML::LibXML. This will be "20602" for libxml2
                        released as "2.6.2" and something like
                        "20602-CVS2032" for a CVS build of
                        libxml2.</para>
                        <para>XML::LibXML issues a warning if the version
                         of libxml2 dynamically linked to it is less than the version of libxml2
                         which it was compiled against.
                         </para>
                    </listitem>
                </varlistentry>

            </variablelist>
        </sect1>
        <sect1>
	  <title>EXPORTS</title>
	  <para>
	    By default the module exports all constants and functions
	    listed in the :all tag, described below.
	  </para>
	</sect1>
        <sect1>
	  <title>EXPORT TAGS</title>
	  <variablelist>
	    <varlistentry>
	      <term><literal>:all</literal></term>
	      <listitem>
		<para>Includes the tags <literal>:libxml</literal>, <literal>:encoding</literal>, and
		<literal>:ns</literal> described below.</para>
	      </listitem>
	    </varlistentry>
	    <varlistentry>
	      <term><literal>:libxml</literal></term>
	      <listitem>
		<para>Exports integer constants for DOM node types.</para>
		<programlisting>XML_ELEMENT_NODE            =&gt; 1
XML_ATTRIBUTE_NODE          =&gt; 2
XML_TEXT_NODE               =&gt; 3
XML_CDATA_SECTION_NODE      =&gt; 4
XML_ENTITY_REF_NODE         =&gt; 5
XML_ENTITY_NODE             =&gt; 6
XML_PI_NODE                 =&gt; 7
XML_COMMENT_NODE            =&gt; 8
XML_DOCUMENT_NODE           =&gt; 9
XML_DOCUMENT_TYPE_NODE      =&gt; 10
XML_DOCUMENT_FRAG_NODE      =&gt; 11
XML_NOTATION_NODE           =&gt; 12
XML_HTML_DOCUMENT_NODE      =&gt; 13
XML_DTD_NODE                =&gt; 14
XML_ELEMENT_DECL            =&gt; 15
XML_ATTRIBUTE_DECL          =&gt; 16
XML_ENTITY_DECL             =&gt; 17
XML_NAMESPACE_DECL          =&gt; 18
XML_XINCLUDE_START          =&gt; 19
XML_XINCLUDE_END            =&gt; 20</programlisting>
	      </listitem>
	    </varlistentry>
	    <varlistentry>
	      <term><literal>:encoding</literal></term>
	      <listitem>
		<para>Exports two encoding conversion functions from XML::LibXML::Common.</para>
		<programlisting>
encodeToUTF8()
decodeFromUTF8()
		</programlisting>
	      </listitem>
	    </varlistentry>
	    <varlistentry>
	      <term><literal>:ns</literal></term>
	      <listitem>
		<para>Exports two convenience constants: the implicit namespace of the
		reserved <literal>xml:</literal> prefix,
		and the implicit namespace for the reserved <literal>xmlns:</literal> prefix.</para>
		<programlisting>
XML_XML_NS    =&gt; 'http://www.w3.org/XML/1998/namespace'
XML_XMLNS_NS  =&gt; 'http://www.w3.org/2000/xmlns/'
		</programlisting>
	      </listitem>
	    </varlistentry>
	  </variablelist>
	</sect1>
        <sect1>
            <title>Related Modules</title>

            <para>The modules described in this section are not part of the XML::LibXML package itself. As they support some additional features, they are
            mentioned here.</para>

            <variablelist>
                <varlistentry>
                    <term><olink targetdoc="XML::LibXSLT">XML::LibXSLT</olink></term>

                    <listitem>
                        <para>XSLT 1.0 Processor using libxslt and XML::LibXML</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><olink targetdoc="XML::LibXML::Iterator">XML::LibXML::Iterator</olink></term>

                    <listitem>
                        <para>XML::LibXML Implementation of the DOM Traversal Specification</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term><olink targetdoc="XML::CompactTree::XS">XML::CompactTree::XS</olink></term>

                    <listitem>
                        <para>Uses XML::LibXML::Reader to very efficiently to parse XML document
			or element into native Perl data structures, which are less flexible but
			significantly faster to process then DOM.</para>
                    </listitem>
                </varlistentry>

            </variablelist>
        </sect1>

        <sect1>
            <title>XML::LibXML and XML::GDOME</title>

            <para>Note: <emphasis>THE FUNCTIONS DESCRIBED HERE ARE STILL EXPERIMENTAL</emphasis></para>

            <para>Although both modules make use of libxml2's XML capabilities, the DOM implementation of both modules are not compatible. But still it is
            possible to exchange nodes from one DOM to the other. The concept of this exchange is pretty similar to the function cloneNode(): The particular
            node is copied on the low-level to the opposite DOM implementation.</para>

            <para>Since the DOM implementations cannot coexist within one document, one is forced to copy each node that should be used. Because you are always
            keeping two nodes this may cause quite an impact on a machines memory usage.</para>

            <para>XML::LibXML provides two functions to export or import GDOME nodes: import_GDOME() and export_GDOME(). Both function have two parameters: the
            node and a flag for recursive import. The flag works as in cloneNode().</para>

            <para>The two functions allow one to export and import XML::GDOME nodes explicitly, however, XML::LibXML also allows the transparent import of
            XML::GDOME nodes in functions such as appendChild(), insertAfter() and so on. While native nodes are automatically adopted in most functions
            XML::GDOME nodes are always cloned in advance. Thus if the original node is modified after the operation, the node in the XML::LibXML document will
            not have this information.</para>

            <variablelist>
                <varlistentry>
                    <term>import_GDOME</term>

                    <listitem>
                        <funcsynopsis>
                            <funcsynopsisinfo>$libxmlnode = XML::LibXML-&gt;import_GDOME( $node, $deep );</funcsynopsisinfo>
                        </funcsynopsis>

                        <para>This clones an XML::GDOME node to an XML::LibXML node explicitly.</para>
                    </listitem>
                </varlistentry>

                <varlistentry>
                    <term>export_GDOME</term>

                    <listitem>
                        <funcsynopsis>
                            <funcsynopsisinfo>$gdomenode = XML::LibXML-&gt;export_GDOME( $node, $deep );</funcsynopsisinfo>
                        </funcsynopsis>

                        <para>Allows one to clone an XML::LibXML node into an
                            XML::GDOME node.</para>

                    </listitem>
                </varlistentry>
            </variablelist>
        </sect1>
        <sect1>
            <title>CONTACTS</title>

            <para>For bug reports, please use the CPAN request tracker on http://rt.cpan.org/NoAuth/Bugs.html?Dist=XML-LibXML</para>
            <para>For suggestions etc., and other issues
	    related to XML::LibXML you may use the perl XML mailing list
            (<email>perl-xml@listserv.ActiveState.com</email>),
	    where most XML-related Perl modules are discussed.
	    In case of problems you should check the archives of that
            list first. Many problems are already discussed there. You
            can find the list's archives and subscription options at
  	    <ulink url="http://aspn.activestate.com/ASPN/Mail/Browse/Threaded/perl-xml">http://aspn.activestate.com/ASPN/Mail/Browse/Threaded/perl-xml</ulink>.
            </para>
        </sect1>
    </chapter>

    <chapter id="XML-LibXML-Parser">
        <title>Parsing XML Data with XML::LibXML</title>

        <titleabbrev>XML::LibXML::Parser</titleabbrev>

        <sect1>
            <title>Synopsis</title>

            <programlisting>use XML::LibXML '1.70';
<!--
my $dom = XML::LibXML-&gt;load_xml(
 location => $file_or_url,
 # or string => $xml_string,
 # or IO => $perl_file_handle,
 # ...parser options...
);

my $html_dom = XML::LibXML-&gt;load_html(
 location => $file_or_url,
 # or string => $html_string,
 # or IO => $perl_file_handle,
 # ...parser options...
);

my $parser = XML::LibXML-&gt;new(
  # ... parser options ...
);

my $doc = $parser-&gt;parse_string(&lt;&lt;'EOT');
&lt;some-xml/&gt;
EOT
my $fdoc = $parser-&gt;parse_file( $xmlfile );

my $fhdoc = $parser-&gt;parse_fh( $xmlstream );

my $fragment = $parser-&gt;parse_xml_chunk( $xml_wb_chunk );
--></programlisting>
        </sect1>

        <sect1>
            <title>Parsing</title>

            <para>An XML document is read into a data structure such as a DOM tree by a piece of software, called a parser. XML::LibXML currently provides four
            different parser interfaces:</para>

            <itemizedlist>
                <listitem>
                    <para>A DOM Pull-Parser</para>
                </listitem>

                <listitem>
                    <para>A DOM Push-Parser</para>
                </listitem>

                <listitem>
                    <para>A SAX Parser</para>
                </listitem>

                <listitem>
                    <para>A DOM based SAX Parser.</para>
                </listitem>
            </itemizedlist>

	    <sect2>
                <title>Creating a Parser Instance</title>

                <para>XML::LibXML provides an OO interface to the libxml2 parser functions. Thus you have to create a parser instance before you can parse any
                XML data.</para>

                <variablelist>
                    <varlistentry>
                        <term>new</term>

                        <listitem>
			    <funcsynopsis role="synopsis">
			       <funcsynopsisinfo># Parser constructor</funcsynopsisinfo>
			    </funcsynopsis>
                            <funcsynopsis>
                                <funcsynopsisinfo>
$parser = XML::LibXML-&gt;new();
$parser = XML::LibXML-&gt;new(option=>value, ...);
$parser = XML::LibXML-&gt;new({option=>value, ...});</funcsynopsisinfo>
                            </funcsynopsis>

                            <para>Create a new XML and HTML parser instance.
			      Each parser instance holds default
			      values for various parser options.
			      Optionally,
			      one can pass a hash reference or
			      a list of option => value pairs to
			      set a different default set of options.
			      Unless specified otherwise, the options
			      <literal>load_ext_dtd</literal>, and
			      <literal>expand_entities</literal> are set to 1.
			      See <xref linkend="parser-options"/> for a list of libxml2 parser's options.
			    </para>
                        </listitem>
                    </varlistentry>
                </variablelist>
            </sect2>

            <sect2>
                <title>DOM Parser</title>

                <para>One of the common parser interfaces of XML::LibXML is the DOM parser. This parser reads XML data into a DOM like data structure, so each
                tag can get accessed and transformed.</para>

                <para>XML::LibXML's DOM parser is not only capable to parse XML data, but also (strict) HTML files. There are three ways to parse
                documents - as a string, as a Perl filehandle, or as a filename/URL. The return value from each is a <xref linkend="XML-LibXML-Document"/> object, which is a DOM
                object.</para>

		<para>All of the functions listed below will throw an exception if the document is invalid. To prevent this causing your program exiting, wrap
                the call in an eval{} block</para>

                <variablelist>
                    <varlistentry>
                        <term>load_xml</term>
                        <listitem>
			  <funcsynopsis role="synopsis">
			       <funcsynopsisinfo>
# Parsing XML</funcsynopsisinfo>
			  </funcsynopsis>
			  <funcsynopsis>
                          <funcsynopsisinfo>
$dom = XML::LibXML-&gt;load_xml(
    location => $file_or_url
    # parser options ...
  );
$dom = XML::LibXML-&gt;load_xml(
    string => $xml_string
    # parser options ...
  );
$dom = XML::LibXML-&gt;load_xml(
    string => (\$xml_string)
    # parser options ...
  );
$dom = XML::LibXML-&gt;load_xml({
    IO => $perl_file_handle
    # parser options ...
  );
$dom = $parser-&gt;load_xml(...);
			  </funcsynopsisinfo>
			  </funcsynopsis>
			  <para>This function is available since XML::LibXML 1.70. It provides easy to use interface to the XML parser that parses
			  given file (or URL), string, or input stream
			  to a DOM tree. The arguments
			  can be passed in a HASH reference
			  or as name => value pairs.
			  The function can be called
			  as a class method or an object method.
			  In both cases it internally creates a new
			  parser instance passing
			  the specified parser options;
			  if called as an object method,
			  it clones the original parser (preserving
			  its settings) and additionally applies
			  the specified options to the new parser.
			  See the constructor <function>new</function>
			  and <xref linkend="parser-options"/>
			  for more information.
			  </para>
			  </listitem>
		    </varlistentry>
                    <varlistentry>
                        <term>load_html</term>
                        <listitem>
			    <funcsynopsis role="synopsis">
			       <funcsynopsisinfo># Parsing HTML</funcsynopsisinfo>
			    </funcsynopsis>
			  <funcsynopsis>
                          <funcsynopsisinfo>
$dom = XML::LibXML-&gt;load_html(...);
$dom = $parser-&gt;load_html(...);
			  </funcsynopsisinfo>
			  </funcsynopsis>
			  <para>This function is available since XML::LibXML 1.70. It has the same usage as <function>load_xml</function>,
			  providing interface to the HTML parser.
			  See <function>load_xml</function> for more information.
			  </para>
			</listitem>
		    </varlistentry>
                </variablelist>

                <para>Parsing HTML may cause problems, especially if
                the ampersand ('&amp;') is used. This is a common
                problem if HTML code is parsed that contains links to
                CGI-scripts. Such links cause the parser to throw
                errors. In such cases libxml2 still parses the entire
                document as there was no error, but the error causes
                XML::LibXML to stop the parsing process. However, the
                document is not lost. Such HTML documents should be
                parsed using the <emphasis>recover</emphasis> flag. By
                default recovering is deactivated.</para>

                <para>The functions described above are implemented to
                parse well formed documents. In some cases a program
                gets well balanced XML instead of well formed
                documents (e.g. an XML fragment from a database). With
                XML::LibXML it is not required to wrap such fragments
                in the code, because XML::LibXML is capable even to
                parse well balanced XML fragments.</para>

                <variablelist>
                    <varlistentry>
                        <term>parse_balanced_chunk</term>
                        <listitem>
			    <funcsynopsis role="synopsis">
			       <funcsynopsisinfo># Parsing well-balanced XML chunks
			       </funcsynopsisinfo>
			    </funcsynopsis>
                            <funcsynopsis>
                                <funcsynopsisinfo>$fragment = $parser-&gt;parse_balanced_chunk( $wbxmlstring, $encoding );</funcsynopsisinfo>
                            </funcsynopsis>

                            <para>This function parses a well balanced XML string into a <xref linkend="XML-LibXML-DocumentFragment"/>. The first arguments contains the input string, the optional second argument can be used to specify character encoding of the input (UTF-8 is assumed by default).</para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>parse_xml_chunk</term>

                        <listitem>
                            <para>This is the old name of parse_balanced_chunk(). Because it may causes confusion with the push parser interface, this function
                            should not be used anymore.</para>
                        </listitem>
                    </varlistentry>
                </variablelist>

                <para>By default XML::LibXML does not process XInclude tags
                    within an XML Document (see options section below).
                    XML::LibXML allows one to post-process a document to expand
                    XInclude tags.</para>

                <variablelist>
                    <varlistentry>
                        <term>process_xincludes</term>
                        <listitem>
			  <funcsynopsis role="synopsis">
			    <funcsynopsisinfo>
# Processing XInclude
</funcsynopsisinfo>
			  </funcsynopsis>
                            <funcsynopsis>
                                <funcsynopsisinfo>$parser-&gt;process_xincludes( $doc );</funcsynopsisinfo>
                            </funcsynopsis>

                            <para>After a document is parsed into a DOM structure, you may want to expand the documents XInclude tags. This function processes
                            the given document structure and expands all XInclude tags (or throws an error) by using the flags and callbacks of the given parser
                            instance.</para>

                            <para>Note that the resulting Tree contains some extra nodes (of type XML_XINCLUDE_START and XML_XINCLUDE_END) after successfully
                            processing the document. These nodes indicate where data was included into the original tree. if the document is serialized, these
                            extra nodes will not show up.</para>

                            <para>Remember: A Document with processed XIncludes differs from the original document after serialization, because the original
                            XInclude tags will not get restored!</para>

                            <para>If the parser flag "expand_xincludes" is set to 1, you need not to post process the parsed document.</para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>processXIncludes</term>

                        <listitem>
                            <funcsynopsis>
                                <funcsynopsisinfo>$parser-&gt;processXIncludes( $doc );</funcsynopsisinfo>
                            </funcsynopsis>

                            <para>This is an alias to process_xincludes, but through a JAVA like function name.</para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>parse_file</term>

                        <listitem>
			    <funcsynopsis role="synopsis">
			       <funcsynopsisinfo>
# Old-style parser interfaces
			       </funcsynopsisinfo>
			    </funcsynopsis>
                            <funcsynopsis>
                                <funcsynopsisinfo>$doc = $parser-&gt;parse_file( $xmlfilename );</funcsynopsisinfo>
                            </funcsynopsis>

                            <para>This function parses an XML document from a file or network;
		              $xmlfilename can be either a filename or an URL.
                              Note that for parsing files, this function is the fastest choice,
		              about 6-8 times faster then parse_fh().
	                     </para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>parse_fh</term>

                        <listitem>
                            <funcsynopsis>
                                <funcsynopsisinfo>$doc = $parser-&gt;parse_fh( $io_fh );</funcsynopsisinfo>
                            </funcsynopsis>

                            <para>parse_fh() parses a IOREF or a subclass of IO::Handle.</para>

                            <para>Because the data comes from an open handle, libxml2's parser does not know about the base URI of the document. To set the
                            base URI one should use parse_fh() as follows:</para>

                            <programlisting>my $doc = $parser-&gt;parse_fh( $io_fh, $baseuri );</programlisting>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>parse_string</term>

                        <listitem>
                            <funcsynopsis>
                                <funcsynopsisinfo>$doc = $parser-&gt;parse_string( $xmlstring);</funcsynopsisinfo>
                            </funcsynopsis>

                            <para>This function is similar to parse_fh(), but it parses an XML document that is available as a single string in memory, or alternatively as a reference to a scalar containing a string. Again,
                            you can pass an optional base URI to the function.</para>

                            <programlisting>my $doc = $parser-&gt;parse_string( $xmlstring, $baseuri );
my $doc = $parser-&gt;parse_string(\$xmlstring, $baseuri);
                            </programlisting>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>parse_html_file</term>

                        <listitem>
                            <funcsynopsis>
                                <funcsynopsisinfo>$doc = $parser-&gt;parse_html_file( $htmlfile, \%opts );</funcsynopsisinfo>
                            </funcsynopsis>

                            <para>Similar to parse_file() but parses HTML (strict) documents;
		               $htmlfile can be filename or URL.
                            </para>
                            <para>An optional second argument can be
                               used to pass some options to the HTML
                               parser as a HASH reference.
			       See options labeled with HTML in <xref linkend="parser-options"/>.
	                    </para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>parse_html_fh</term>

                        <listitem>
                            <funcsynopsis>
                                <funcsynopsisinfo>$doc = $parser-&gt;parse_html_fh( $io_fh, \%opts );</funcsynopsisinfo>
                            </funcsynopsis>
                            <para>Similar to parse_fh() but parses HTML (strict) streams.</para>
                            <para>
                               An optional second argument can be used
                               to pass some options to the HTML parser
                               as a HASH reference.
			       See options labeled with HTML in <xref linkend="parser-options"/>.
			    </para>
			    <para>
			       Note: encoding option may
                               not work correctly with this function
                               in libxml2 &lt; 2.6.27 if the HTML file
                               declares charset using a META tag.
	                    </para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>parse_html_string</term>

                        <listitem>
                            <funcsynopsis>
                                <funcsynopsisinfo>$doc = $parser-&gt;parse_html_string( $htmlstring, \%opts );</funcsynopsisinfo>
                            </funcsynopsis>
                            <para>Similar to parse_string() but parses HTML (strict) strings.</para>
                            <para>An optional second argument can be used to pass some options to the
                               HTML parser as a HASH reference.
			       See options labeled with HTML in <xref linkend="parser-options"/>.
	                    </para>
                        </listitem>
                    </varlistentry>
                </variablelist>
            </sect2>

            <sect2>
                <title>Push Parser</title>

                <para>XML::LibXML provides a push parser interface. Rather than pulling the data from a given source the push parser waits for the data to be
                pushed into it.</para>

                <para>This allows one to parse large documents without waiting for the parser to finish. The interface is especially useful if a program needs
                to pre-process the incoming pieces of XML (e.g. to detect document boundaries).</para>

                <para>While XML::LibXML parse_*() functions force the data to be a well-formed XML, the push parser will take any arbitrary string that contains
                some XML data. The only requirement is that all the pushed strings are together a well formed document. With the push parser interface a
                program can interrupt the parsing process as required, where the parse_*() functions give not enough flexibility.</para>

                <para>Different to the pull parser implemented in parse_fh() or parse_file(), the push parser is not able to find out about the documents end
                itself. Thus the calling program needs to indicate explicitly when the parsing is done.</para>

                <para>In XML::LibXML this is done by a single function:</para>

                <variablelist>
                    <varlistentry>
                        <term>parse_chunk</term>

                        <listitem>
			  <funcsynopsis role="synopsis">
			    <funcsynopsisinfo>
# Push parser
			    </funcsynopsisinfo>
			  </funcsynopsis>
                            <funcsynopsis>
                                <funcsynopsisinfo>$parser-&gt;parse_chunk($string, $terminate);</funcsynopsisinfo>
                            </funcsynopsis>

                            <para>parse_chunk() tries to parse a given chunk of data, which isn't necessarily well balanced data. The function takes two
                            parameters: The chunk of data as a string and optional a termination flag. If the termination flag is set to a true value (e.g. 1),
                            the parsing will be stopped and the resulting document will be returned as the following example describes:</para>

                            <programlisting>my $parser = XML::LibXML-&gt;new;
for my $string ( "&lt;", "foo", ' bar="hello world"', "/&gt;") {
     $parser-&gt;parse_chunk( $string );
}
my $doc = $parser-&gt;parse_chunk("", 1); # terminate the parsing</programlisting>
                        </listitem>
                    </varlistentry>
                </variablelist>

                <para>Internally XML::LibXML provides three functions that control the push parser process:</para>

                <variablelist>
                    <varlistentry>
                        <term>init_push</term>

                        <listitem>
                            <funcsynopsis>
                                <funcsynopsisinfo>$parser-&gt;init_push();</funcsynopsisinfo>
                            </funcsynopsis>

                            <para>Initializes the push parser.</para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>push</term>

                        <listitem>
                            <funcsynopsis>
                                <funcsynopsisinfo>$parser-&gt;push(@data);</funcsynopsisinfo>
                            </funcsynopsis>

                            <para>This function pushes the data stored inside the array to libxml2's parser. Each entry in @data must be a normal scalar! This method can be called repeatedly.</para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>finish_push</term>

                        <listitem>
                            <funcsynopsis>
                                <funcsynopsisinfo>$doc = $parser-&gt;finish_push( $recover );</funcsynopsisinfo>
                            </funcsynopsis>

                            <para>This function returns the result of the parsing process. If this function is called without a parameter it will complain about
                            non well-formed documents. If $restore is 1, the push parser can be used to restore broken or non well formed (XML) documents as the
                            following example shows:</para>

                            <programlisting>eval {
    $parser-&gt;push( "&lt;foo&gt;", "bar" );
    $doc = $parser-&gt;finish_push();    # will report broken XML
};
if ( $@ ) {
   # ...
}</programlisting>

                            <para>This can be annoying if the closing tag is missed by accident. The following code will restore the document:</para>

                            <programlisting>eval {
    $parser-&gt;push( "&lt;foo&gt;", "bar" );
    $doc = $parser-&gt;finish_push(1);   # will return the data parsed
                                      # unless an error happened
};

print $doc-&gt;toString(); # returns "&lt;foo&gt;bar&lt;/foo&gt;"</programlisting>

                            <para>Of course finish_push() will return nothing if there was no data pushed to the parser before.</para>
                        </listitem>
                    </varlistentry>
                </variablelist>
            </sect2>

            <sect2>
                <title>Pull Parser (Reader)</title>
                <para>XML::LibXML also provides a pull-parser interface similar to the XmlReader interface in .NET.
		This interface is almost streaming, and is usually faster and simpler to use than SAX.
		See <xref linkend="XML-LibXML-Reader"/>.</para>
	    </sect2>

            <sect2>
                <title>Direct SAX Parser</title>
                <para>XML::LibXML provides a direct SAX parser in the <xref linkend="XML-LibXML-SAX"/> module.</para>
	    </sect2>

            <sect2>
                <title>DOM based SAX Parser</title>

                <para>XML::LibXML also provides a DOM based SAX parser. The SAX parser is defined in
		the module XML::LibXML::SAX::Parser. As it is not a stream based parser, it
                parses documents into a DOM and traverses the DOM tree instead.</para>

                <para>The API of this parser is exactly the same as any other Perl SAX2 parser. See XML::SAX::Intro for details.</para>

                <para>Aside from the regular parsing methods, you can access the DOM tree traverser directly, using the generate() method:</para>

                <programlisting>my $doc = build_yourself_a_document();
my $saxparser = $XML::LibXML::SAX::Parser-&gt;new( ... );
$parser-&gt;generate( $doc );</programlisting>

                <para>This is useful for serializing DOM trees, for example that you might have done prior processing on, or that you have as a result of XSLT
                processing.</para>

                <para><emphasis>WARNING</emphasis></para>

                <para>This is NOT a streaming SAX parser. As I said above, this parser reads the entire document into a DOM and serialises it. Some people
                couldn't read that in the paragraph above so I've added this warning. If you want a streaming SAX parser look at the <xref linkend="XML-LibXML-SAX"/> man page</para>
            </sect2>
        </sect1>

        <sect1>
            <title>Serialization</title>

            <para>XML::LibXML provides some functions to serialize nodes and documents. The serialization functions are described on the <xref linkend="XML-LibXML-Node"/>
            manpage or the <xref linkend="XML-LibXML-Document"/> manpage. XML::LibXML checks three global flags that alter the serialization process:</para>

            <itemizedlist>
                <listitem>
                    <para>skipXMLDeclaration</para>
                </listitem>

                <listitem>
                    <para>skipDTD</para>
                </listitem>

                <listitem>
                    <para>setTagCompression</para>
                </listitem>
            </itemizedlist>

            <para>of that three functions only setTagCompression is available for all serialization functions.</para>

            <para>Because XML::LibXML does these flags not itself, one has to define them locally as the following example shows:</para>

            <programlisting>local $XML::LibXML::skipXMLDeclaration = 1;
local $XML::LibXML::skipDTD = 1;
local $XML::LibXML::setTagCompression = 1;</programlisting>

            <para>If skipXMLDeclaration is defined and not '0', the XML declaration is omitted during serialization.</para>

            <para>If skipDTD is defined and not '0', an existing DTD would not be serialized with the document.</para>

            <para>If setTagCompression is defined and not '0' empty tags are displayed as open and closing tags rather than the shortcut. For example
            the empty tag <emphasis>foo</emphasis> will be rendered as <emphasis>&lt;foo&gt;&lt;/foo&gt;</emphasis> rather than <emphasis>&lt;foo/&gt;</emphasis>.</para>
        </sect1>

        <sect1 id="parser-options">
            <title>Parser Options</title>

	    <para>Handling of libxml2 parser options has been unified and improved in XML::LibXML 1.70.
	      You can now set default options for a particular parser instance by
	      passing them to the constructor as <literal>XML::LibXML->new({name=>value, ...})</literal>
	      or <literal>XML::LibXML->new(name=>value,...)</literal>.
	      The options can be queried and changed using the following methods (pre-1.70 interfaces such as <function>$parser->load_ext_dtd(0)</function> also exist, see below):
	    </para>

            <variablelist>
              <varlistentry>
                <term>option_exists</term>
                <listitem>
		  <funcsynopsis role="synopsis">
		    <funcsynopsisinfo>
# Set/query parser options
                    </funcsynopsisinfo>
		  </funcsynopsis>
                  <funcsynopsis>
                    <funcsynopsisinfo>$parser-&gt;option_exists($name);</funcsynopsisinfo>
                  </funcsynopsis>
                  <para>Returns 1 if the current XML::LibXML version supports
		    the option <literal>$name</literal>, otherwise returns 0 (note that this does not necessarily mean that the option is supported
		    by the underlying libxml2 library).</para>
                </listitem>
	      </varlistentry>
	      <varlistentry>
                <term>get_option</term>
                <listitem>
                  <funcsynopsis>
                    <funcsynopsisinfo>$parser-&gt;get_option($name);</funcsynopsisinfo>
                  </funcsynopsis>
                  <para>Returns the current value of the parser option <literal>$name</literal>.</para>
                </listitem>
              </varlistentry>
	      <varlistentry>
                <term>set_option</term>
                <listitem>
                  <funcsynopsis>
                    <funcsynopsisinfo>$parser-&gt;set_option($name,$value);</funcsynopsisinfo>
                  </funcsynopsis>
                  <para>Sets option <literal>$name</literal> to value <literal>$value</literal>.</para>
                </listitem>
              </varlistentry>
	      <varlistentry>
                <term>set_options</term>
                <listitem>
                  <funcsynopsis>
                    <funcsynopsisinfo>$parser-&gt;set_options({$name=>$value,...});</funcsynopsisinfo>
                  </funcsynopsis>
                  <para>Sets multiple parsing options at once.</para>
                </listitem>
              </varlistentry>
	    </variablelist>
	    <para>
	      IMPORTANT NOTE: This documentation reflects the parser flags available in libxml2 2.7.3.
	      Some options have no effect if an older version of libxml2 is used.
	    </para>
	    <para>Each of the flags listed below is labeled</para>
	    <variablelist>
	      <varlistentry>
		<term>/parser/</term>
		<listitem>
		  <para>if it can be used with a <function>XML::LibXML</function>
		  parser object (i.e. passed to <function>XML::LibXML->new</function>, <function>XML::LibXML->set_option</function>, etc.)
		  </para>
		</listitem>
	      </varlistentry>
	      <varlistentry>
		<term>/html/</term>
		<listitem>
		  <para>if it can be used passed to the <function>parse_html_*</function> methods</para>
		</listitem>
	      </varlistentry>
	      <varlistentry>
		<term>/reader/</term>
		<listitem>
		  <para>if it can be used with the <function>XML::LibXML::Reader</function>.</para>
		</listitem>
	      </varlistentry>
	    </variablelist>
	    <para>
	      Unless specified otherwise, the default for boolean valued options is 0 (false).
	    </para>
	      <para>The available options are:</para>
	    <variablelist>
          <varlistentry>
            <term>URI</term>
            <listitem>
	      <para>/parser, html, reader/</para>
              <para>In case of parsing strings or file handles, XML::LibXML doesn't know about the base uri of the document. To make relative
                references such as XIncludes work, one has to set a base URI, that is then used for the parsed document.</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>line_numbers</term>
            <listitem>
	      <para>/parser, html, reader/</para>
              <para>If this option is activated, libxml2 will store the line number of each element node in the parsed document.
		The line number can be obtained using the <function>line_number()</function> method
		of the <function>XML::LibXML::Node</function> class (for non-element nodes
		this may report the line number of the containing element).
		The line numbers are also used for reporting positions of validation errors.
	      </para>
	      <para>IMPORTANT:
		Due to limitations in the libxml2 library line numbers greater than
		65535 will be returned as 65535. Unfortunately, this is a long and sad story, please see
		<ulink url="http://bugzilla.gnome.org/show_bug.cgi?id=325533">http://bugzilla.gnome.org/show_bug.cgi?id=325533</ulink> for more details.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>encoding</term>
            <listitem>
	      <para>/html/</para>
              <para>character encoding of the input</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>recover</term>
            <listitem>
	      <para>/parser, html, reader/</para>
              <para>recover from errors; possible values are 0, 1, and 2</para>
              <para>
		A true value turns on recovery mode which
		allows one to parse broken XML or HTML data.
		The recovery mode allows the parser to return
		the successfully parsed portion of the input document.
		This is useful for almost well-formed documents, where for example
		a closing tag is missing somewhere. Still,
		XML::LibXML will only parse until the first fatal (non-recoverable) error occurs,
		reporting recoverable parsing errors as warnings. To suppress
                even these warnings, use recover=>2.</para>
	      <para>Note that validation is switched off automatically in recovery mode.</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>expand_entities</term>
            <listitem>
	      <para>/parser, reader/</para>
              <para>substitute entities; possible values are 0 and 1; default is 1</para>
	      <para>Note that although this flag disables entity substitution, it
	      does not prevent the parser from loading external entities;
	      when substitution of an external entity is disabled, the
	      entity will be represented in the document tree by an XML_ENTITY_REF_NODE node
	      whose subtree will be the content obtained by parsing the external resource;
	      Although this nesting is visible from the DOM
	      it is transparent to XPath data model, so it is possible to
	      match nodes in an unexpanded entity by the same XPath expression
	      as if the entity were expanded. See also ext_ent_handler.
	      </para>
	    </listitem>
	  </varlistentry>
          <varlistentry>
            <term>ext_ent_handler</term>
            <listitem>
	      <para>/parser/</para>
	      <para>Provide a custom external entity handler
	      to be used when expand_entities is set to 1.
	      Possible value is a subroutine reference.
	      </para>
	      <para>This feature does not work properly in libxml2 &lt; 2.6.27!</para>
	      <para>The subroutine provided is called whenever
	      the parser needs to retrieve the content of an external entity.
	      It is called with two arguments: the system ID (URI) and the public ID.
	      The value returned by the subroutine is parsed as the content of the entity.
	      </para>
	      <para>This method can be used to completely disable entity loading,
	      e.g. to prevent exploits of the type described at
	      <ulink url="http://searchsecuritychannel.techtarget.com/generic/0,295582,sid97_gci1304703,00.html"/>,
	      where a service is tricked to expose its private data
	      by letting it parse a remote file (RSS feed) that contains an entity reference to a local
	      file (e.g. <literal>/etc/fstab</literal>).
	      </para>
	      <para>A more granular solution to this problem, however, is
	      provided by custom URL resolvers, as in
	      <programlisting>
my $c = XML::LibXML::InputCallback->new();
sub match {   # accept file:/ URIs except for XML catalogs in /etc/xml/
  my ($uri) = @_;
  return ($uri=~m{^file:/}
          and $uri !~ m{^file:///etc/xml/})
         ? 1 : 0;
}
$c->register_callbacks([ \&amp;match, sub{}, sub{}, sub{} ]);
$parser->input_callbacks($c);
	      </programlisting>
	      </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>load_ext_dtd</term>
            <listitem>
	      <para>/parser, reader/</para>
              <para>load the external DTD subset while parsing; possible values are 0 and 1. Unless specified,
		XML::LibXML sets this option to 1.</para>
              <para>This flag is also required for DTD Validation, to provide complete attribute,
                and to expand entities, regardless if the document has an internal subset.
                Thus switching off external DTD loading, will disable entity expansion,
                validation, and complete attributes on internal subsets as well.</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>complete_attributes</term>
            <listitem>
	      <para>/parser, reader/</para>
              <para>create default DTD attributes; possible values are 0 and 1</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>validation</term>
            <listitem>
	      <para>/parser, reader/</para>
              <para>validate with the DTD; possible values are 0 and 1</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>suppress_errors</term>
            <listitem>
	      <para>/parser, html, reader/</para>
              <para>suppress error reports; possible values are 0 and 1</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>suppress_warnings</term>
            <listitem>
	      <para>/parser, html, reader/</para>
              <para>suppress warning reports; possible values are 0 and 1</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>pedantic_parser</term>
            <listitem>
	      <para>/parser, html, reader/</para>
              <para>pedantic error reporting; possible values are 0 and 1</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>no_blanks</term>
            <listitem>
	      <para>/parser, html, reader/</para>
              <para>remove blank nodes; possible values are 0 and 1</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>no_defdtd</term>
            <listitem>
	      <para>/html/</para>
              <para>do not add a default DOCTYPE; possible values are 0 and 1</para>
              <para>the default is (0) to add a DTD when the input html lacks one</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>expand_xinclude or xinclude</term>
            <listitem>
	      <para>/parser, reader/</para>
              <para>Implement XInclude substitution; possible values are 0 and 1</para>
              <para>Expands XInclude tags immediately while parsing the document.
		Note that the parser will use the URI resolvers installed
		via <function>XML::LibXML::InputCallback</function> to parse the included document (if any).</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>no_xinclude_nodes</term>
            <listitem>
	      <para>/parser, reader/</para>
              <para>do not generate XINCLUDE START/END nodes; possible values are 0 and 1</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>no_network</term>
            <listitem>
	      <para>/parser, html, reader/</para>
              <para>Forbid network access; possible values are 0 and 1</para>
              <para>If set to true, all
                attempts to fetch non-local resources (such as
                DTD or external entities) will fail (unless
                custom callbacks are defined).</para>
	      <para>It may be
                necessary to use the flag <literal>recover</literal> for
                processing documents requiring such resources
                while networking is off.
              </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>clean_namespaces</term>
            <listitem>
	      <para>/parser, reader/</para>
              <para>remove redundant namespaces declarations during parsing; possible values are 0 and 1.
	      </para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>no_cdata</term>
            <listitem>
	      <para>/parser, html, reader/</para>
              <para>merge CDATA as text nodes; possible values are 0 and 1</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>no_basefix</term>
            <listitem>
	      <para>/parser, reader/</para>
              <para>not fixup XINCLUDE xml#base URIS; possible values are 0 and 1</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>huge</term>
            <listitem>
	      <para>/parser, html, reader/</para>
              <para>relax any hardcoded limit from the parser; possible values are 0 and 1. Unless specified,
		XML::LibXML sets this option to 0.</para>
              <para>Note: the default value for this option was changed to protect against denial
                of service through entity expansion attacks.  Before enabling the option ensure
                you have taken alternative measures to protect your application against this type
                of attack.</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>gdome</term>
            <listitem>
	      <para>/parser/</para>
              <para>THIS OPTION IS EXPERIMENTAL!</para>
              <para>Although quite powerful, XML::LibXML's DOM implementation is incomplete with respect to
		the DOM level 2 or level 3 specifications.
                XML::GDOME is based on libxml2 as well, and provides a rather complete DOM implementation by wrapping libgdome.
		This flag allows you to make
                use of XML::LibXML's full parser options and XML::GDOME's DOM implementation at the same time.</para>
              <para>To make use of this function, one has to install libgdome and configure XML::LibXML to use this library.
		For this you need to rebuild XML::LibXML!</para>
	      <para>Note: this feature was not seriously tested in recent XML::LibXML releases.</para>
            </listitem>
	  </varlistentry>
	</variablelist>
	    <para>For compatibility with XML::LibXML versions prior to 1.70,
	      the following methods are also supported for querying and setting the corresponding parser options
	      (if called without arguments, the methods return
	      the current value of the corresponding parser options; with an argument sets the option to a given value):
	    </para>
	    <programlisting>$parser->validation();
$parser->recover();
$parser->pedantic_parser();
$parser->line_numbers();
$parser->load_ext_dtd();
$parser->complete_attributes();
$parser->expand_xinclude();
$parser->gdome_dom();
$parser->clean_namespaces();
$parser->no_network();</programlisting>
	    <para>The following obsolete methods trigger parser options in some
	      special way:</para>
	    <variablelist>
                <varlistentry>
                    <term>recover_silently</term>
                    <listitem>
                        <programlisting>
                            $parser-&gt;recover_silently(1);
                        </programlisting>
                        <para>If called without an argument,
			  returns true if the current value of the <literal>recover</literal> parser
			  option is 2 and returns false otherwise.
			  With a true argument sets the <literal>recover</literal> parser option to 2;
			  with a false argument sets the <literal>recover</literal> parser option to 0.
			</para>
                    </listitem>
                </varlistentry>
                <varlistentry>
                    <term>expand_entities</term>
                    <listitem>
                        <programlisting>
                            $parser-&gt;expand_entities(0);
                        </programlisting>
                        <para>Get/set the <literal>expand_entities</literal> option.
			  If called with a true argument, also turns
			  the <literal>load_ext_dtd</literal> option to 1.
			</para>
                    </listitem>
                </varlistentry>
                <varlistentry>
                    <term>keep_blanks</term>
                    <listitem>
                        <programlisting>
                            $parser-&gt;keep_blanks(0);
                        </programlisting>
                        <para>This is actually the opposite of the <literal>no_blanks</literal> parser option.
			  If used without an argument retrieves negated value of <literal>no_blanks</literal>.
			  If used with an argument sets <literal>no_blanks</literal> to the opposite value.
			</para>
                    </listitem>
                </varlistentry>
                <varlistentry>
                    <term>base_uri</term>

                    <listitem>
                        <programlisting>
                            $parser-&gt;base_uri( $your_base_uri );
                        </programlisting>
                        <para>Get/set the <literal>URI</literal> option.</para>
                    </listitem>
                </varlistentry>
            </variablelist>
        </sect1>
        <sect1>
            <title>XML Catalogs</title>
	    <para><literal>libxml2</literal> supports XML catalogs.
		Catalogs are used to
		map remote resources to their local copies.
		Using catalogs can speed up parsing processes if
                many external resources from remote addresses
		are loaded into the parsed documents (such as DTDs or XIncludes).
	      </para>
	      <para>
		Note that libxml2 has a global pool of loaded catalogs,
		so if you apply the method <literal>load_catalog</literal>
		to one parser instance, all parser instances will start using the catalog
		(in addition to other previously loaded catalogs).
	      </para>
	      <para>Note also that catalogs are not used
                when a custom external entity handler is specified. At the
                current state it is not possible to make use of both
                types of resolving systems at the same time.</para>
		<variablelist>
              <varlistentry>
                <term>load_catalog</term>
                <listitem>
		  <funcsynopsis role="synopsis">
		    <funcsynopsisinfo>
# XML catalogs
                    </funcsynopsisinfo>
		  </funcsynopsis>
                  <funcsynopsis>
                    <funcsynopsisinfo>$parser-&gt;load_catalog( $catalog_file );</funcsynopsisinfo>
                  </funcsynopsis>
		  <para>Loads the XML catalog file $catalog_file.</para>
          <programlisting>
# Global external entity loader (similar to ext_ent_handler option
# but this works really globally, also in XML::LibXSLT include etc..)

XML::LibXML::externalEntityLoader(\&amp;my_loader);
          </programlisting>
		</listitem>
	      </varlistentry>
		</variablelist>
	      </sect1>
              <sect1>
            <title>Error Reporting</title>

            <para>XML::LibXML throws exceptions during parsing, validation or XPath processing (and some other occasions). These errors can be caught by using
            <emphasis>eval</emphasis> blocks. The error is stored in <emphasis>$@</emphasis>.
	    There are two implementations: the old one throws $@ which is just a message string,
	    in the new one $@ is an object from the class XML::LibXML::Error;
	    this class overrides the operator "" so that when printed,
	    the object flattens to the usual error message.
	    </para>

            <para>XML::LibXML throws errors as they occur. This is a very common misunderstanding in the use of XML::LibXML. If the eval is omitted, XML::LibXML will always halt your script by
            "croaking" (see Carp man page for details).</para>

            <para>Also note that an increasing number of functions throw errors if bad data is passed as arguments. If you cannot assure valid data passed to XML::LibXML you should eval
            these functions.</para>

            <para>Note: since version 1.59, get_last_error() is no longer available in XML::LibXML for thread-safety reasons.</para>
        </sect1>
    </chapter>

    <chapter id="XML-LibXML-SAX">
        <title>XML::LibXML direct SAX parser</title>

        <titleabbrev>XML::LibXML::SAX</titleabbrev>

        <sect1>
            <title>Description</title>

            <para>XML::LibXML provides an interface to libxml2 direct SAX interface. Through this interface it is possible to generate SAX events directly while
            parsing a document. While using the SAX parser XML::LibXML will not create a DOM Document tree.</para>

            <para>Such an interface is useful if very large XML documents have to be processed and no DOM functions are required. By using this interface it is
            possible to read data stored within an XML document directly into the application data structures without loading the document into memory.</para>

            <para>The SAX interface of XML::LibXML is based on the famous XML::SAX interface. It uses the generic interface as provided by XML::SAX::Base.</para>

            <para>Additionally to the generic functions, which are only able to process entire documents, XML::LibXML::SAX provides <emphasis>parse_chunk()</emphasis>.
            This method generates SAX events from well balanced data such as is often provided by databases.</para>
        </sect1>

        <sect1>
            <title>Features</title>

            <para><emphasis>NOTE:</emphasis> This feature is experimental. </para>

            <para>You can enable character data joining which may yield a
            significant speed boost in your XML processing in lower markup
            ratio situations by enabling the
            http://xmlns.perl.org/sax/join-character-data feature of this
            parser. This is done via the set_feature method like
            this:
            </para>

            <programlisting>$p->set_feature('http://xmlns.perl.org/sax/join-character-data', 1);
            </programlisting>

            <para>
            You can also specify a 0 to disable. The default is to have
            this feature disabled.
            </para>
        </sect1>
    </chapter>

    <chapter id="XML-LibXML-SAX-Builder">
        <title>Building DOM trees from SAX events.</title>

        <titleabbrev>XML::LibXML::SAX::Builder</titleabbrev>

        <sect1>
            <title>Synopsis</title>

            <programlisting>use XML::LibXML::SAX::Builder;
my $builder = XML::LibXML::SAX::Builder-&gt;new();

my $gen = XML::Generator::DBI-&gt;new(Handler =&gt; $builder, dbh =&gt; $dbh);
$gen-&gt;execute("SELECT * FROM Users");

my $doc = $builder-&gt;result();</programlisting>
        </sect1>

        <sect1>
            <title>Description</title>

            <para>This is a SAX handler that generates a DOM tree from SAX events. Usage is as above. Input is accepted from any SAX1 or SAX2 event generator.</para>

            <para>Building DOM trees from SAX events is quite easy with XML::LibXML::SAX::Builder. The class is designed as a SAX2 final handler not as a
            filter!</para>

            <para>Since SAX is strictly stream oriented, you should not expect anything to return from a generator. Instead you have to ask the builder instance
            directly to get the document built. XML::LibXML::SAX::Builder's result() function holds the document generated from the last SAX stream.</para>
        </sect1>
    </chapter>

    <chapter id="XML-LibXML-DOM">
        <title>XML::LibXML DOM Implementation</title>
        <titleabbrev>XML::LibXML::DOM</titleabbrev>
        <sect1>
            <title>Description</title>
            <para>XML::LibXML provides a lightweight interface to
            <emphasis>modify</emphasis> a node of the document tree
            generated by the XML::LibXML parser.  This interface
            follows as far as possible the DOM Level 3
            specification. In addition to the specified functions,
            XML::LibXML supports some functions that are more handy to
            use in the perl environment.</para>

            <para>One also has to remember, that XML::LibXML is an
            interface to libxml2 nodes which actually reside on the
            C-Level of XML::LibXML. This means each node is a
            reference to a structure which is different from a perl hash or
            array. The only way to access these structures' values is
            through the DOM interface provided by XML::LibXML. This
            also means, that one <emphasis>can't</emphasis> simply
            inherit an XML::LibXML node and add new member variables as
            if they were hash keys.</para>

            <para>The DOM interface of XML::LibXML does not intend to
            implement a full DOM interface as it is done by XML::GDOME
            and used for full featured application. Moreover, it
            offers an simple way to build or modify documents that are
            created by XML::LibXML's parser.</para>

            <para>Another target of the XML::LibXML interface is to
            make the interfaces of libxml2 available to the perl
            community. This includes also some workarounds to some
            features where libxml2 assumes more control over the
            C-Level that most perl users don't have.</para>

            <para>One of the most important parts of the XML::LibXML
            DOM interface is that the interfaces try to follow the
            <ulink url="http://www.w3.org/TR/DOM-Level-3-Core/">DOM Level 3 specification</ulink> rather strictly. This means the
            interface functions are named as the DOM specification
            says and not what widespread Java interfaces claim to be
            the standard.  Although there are several functions that have
            only a singular interface that conforms to the DOM spec
            XML::LibXML provides an additional Java style alias
            interface.</para>

            <para>Moreover, there are some function interfaces left over
            from early stages of XML::LibXML for compatibility
            reasons. These interfaces are for compatibility reasons
            <emphasis>only</emphasis>. They might disappear in one of
            the future versions of XML::LibXML, so a user is requested
            to switch over to the official functions.</para>
	    <sect2>
	      <title>Encodings and XML::LibXML's DOM implementation</title>
	    <para>See the section on Encodings in the <emphasis>XML::LibXML</emphasis> manual page.</para>
	    </sect2>
	    <sect2>
	      <title>Namespaces and XML::LibXML's DOM implementation</title>

            <para>XML::LibXML's DOM implementation is
            limited by the DOM implementation of libxml2
            which treats namespaces slightly differently than
            required by the DOM Level 2 specification.
            </para>
            <para>According to the DOM Level 2 specification,
             namespaces of elements and attributes should be
             persistent, and nodes should be permanently bound to
             namespace URIs as they get created; it should be
             possible to manipulate the special attributes used for
             declaring XML namespaces just as other attributes
             without affecting the namespaces of other nodes.
             In DOM Level 2, the application is responsible
             for creating the special attributes consistently and/or for correct
             serialization of the document.
            </para>
            <para>
	     This is both inconvenient, causes problems in serialization
	     of DOM to XML, and most importantly, seems almost impossible
             to implement over libxml2.
            </para>
            <para>
             In libxml2, namespace URI and prefix of a node is
             provided by a pointer to a namespace declaration
             (appearing as a special xmlns attribute in the XML
             document). If the prefix or namespace URI of the
             declaration changes, the prefix and namespace URI of all
             nodes that point to it changes as well.  Moreover, in
             contrast to DOM, a node (element or attribute) can only
             be bound to a namespace URI if there is some namespace
             declaration in the document to point to.
            </para>
            <para>
             Therefore current DOM implementation in XML::LibXML tries
             to treat namespace declarations in a compromise between
             reason, common sense, limitations of libxml2, and the DOM
             Level 2 specification.
            </para>
            <para>In XML::LibXML, special attributes declaring XML namespaces
	     are often created automatically, usually when
	     a namespaced node is attached to a document
             and no existing declaration of the namespace and prefix is in the
             scope to be reused.
             In this respect,
	     XML::LibXML DOM implementation differs from the DOM
             Level 2 specification according to which special
              attributes for declaring the appropriate XML namespaces
              should not be added when a node with a namespace prefix
              and namespace URI is created.
            </para>
            <para>
             Namespace declarations are also created when
             <xref linkend="XML-LibXML-Document"/>'s
             createElementNS() or createAttributeNS() function are used. If the
             a namespace is not declared on the documentElement, the
             namespace will be locally declared for the newly created
             node. In case of Attributes this may look a bit confusing,
	     since these nodes cannot have namespace declarations
	     itself. In this case the namespace is internally applied
	     to the attribute and later declared on the node the
             attribute is appended to (if required).</para>
            <para>The following example may explain this a bit:</para>
            <programlisting>my $doc = XML::LibXML-&gt;createDocument;
my $root = $doc-&gt;createElementNS( "", "foo" );
$doc-&gt;setDocumentElement( $root );

my $attr = $doc-&gt;createAttributeNS( "bar", "bar:foo", "test" );
$root-&gt;setAttributeNodeNS( $attr );</programlisting>

            <para>This piece of code will result in the following document:</para>

            <programlisting>&lt;?xml version="1.0"?&gt;
&lt;foo xmlns:bar="bar" bar:foo="test"/&gt;</programlisting>

            <para>The namespace is declared on the document element
              during the setAttributeNodeNS() call.
            </para>
            <para>Namespaces can be also declared explicitly by the use of XML::LibXML::Element's setNamespace() function.
	     Since 1.61, they can also be manipulated with functions
             setNamespaceDeclPrefix() and setNamespaceDeclURI() (not available in DOM).
	     Changing an URI or prefix of an existing namespace declaration
             affects the namespace URI and prefix of all nodes which point to it
             (that is the nodes in its scope).
            </para>
            <para>It is also important to repeat the specification:
            While working with namespaces you should use the namespace
            aware functions instead of the simplified versions. For
            example you should <emphasis>never</emphasis> use
            setAttribute() but setAttributeNS().</para>
	  </sect2>
        </sect1>
    </chapter>

    <chapter id="XML-LibXML-Document">
        <title>XML::LibXML DOM Document Class</title>

        <titleabbrev>XML::LibXML::Document</titleabbrev>
        <sect1>
            <title>Synopsis</title>
            <programlisting>use XML::LibXML;
# Only methods specific to Document nodes are listed here,
# see the XML::LibXML::Node manpage for other methods</programlisting>
        </sect1>
	<sect1>
            <title>Description</title>
        <para>The Document Class is in most cases the result of a parsing process. But sometimes it is necessary to create a Document from scratch. The DOM
        Document Class provides functions that conform to the DOM Core naming style.</para>

        <para>It inherits all functions from <xref linkend="XML-LibXML-Node"/> as specified in the DOM specification. This enables access to the nodes
        besides the root element on document level - a <function>DTD</function> for example. The support for these nodes is limited at the moment.</para>

        <para>While generally nodes are bound to a document in the DOM concept it is suggested that one should always create a node not bound to any document.
        There is no need of really including the node to the document, but once the node is bound to a document, it is quite safe that all strings have the
        correct encoding. If an unbound text node with an ISO encoded string is created (e.g. with $CLASS-&gt;new()), the <function>toString</function> function
        may not return the expected result.</para>

        <para>To prevent such problems, it is recommended to pass all data to XML::LibXML methods
	as character strings (i.e. UTF-8 encoded, with the UTF8 flag on).</para>
	</sect1>
        <sect1>
            <title>Methods</title>
	    <para>
	      Many functions listed here are
	      extensively documented in the <ulink url="http://www.w3.org/TR/DOM-Level-3-Core/">DOM Level 3 specification</ulink>. Please refer to
	      the specification for extensive documentation.
	    </para>
        <variablelist>
            <varlistentry>
                <term>new</term>
                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$dom = XML::LibXML::Document-&gt;new( $version, $encoding );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>alias for createDocument()</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>createDocument</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$dom = XML::LibXML::Document-&gt;createDocument( $version, $encoding );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The constructor for the document class. As Parameter it takes the version string and (optionally) the encoding string. Simply calling
                    <emphasis>createDocument</emphasis>() will create the document:</para>

                    <programlisting>&lt;?xml version="your version" encoding="your encoding"?&gt;</programlisting>

                    <para>Both parameter are optional. The default value for <emphasis>$version</emphasis> is <function>1.0</function>, of course. If the
                    <emphasis>$encoding</emphasis> parameter is not set, the encoding will be left unset, which means UTF-8 is implied.</para>

                    <para>The call of <emphasis>createDocument</emphasis>() without any parameter will result the following code:</para>

                    <programlisting>&lt;?xml version="1.0"?&gt;              </programlisting>

                    <para>Alternatively one can call this constructor directly from the XML::LibXML class level, to avoid some typing. This will not have any
                    effect on the class instance, which is always XML::LibXML::Document.</para>

                    <programlisting> my $document = XML::LibXML-&gt;createDocument( "1.0", "UTF-8" );</programlisting>

                    <para>is therefore a shortcut for</para>

                    <programlisting>my $document = XML::LibXML::Document-&gt;createDocument( "1.0", "UTF-8" );</programlisting>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>URI</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$strURI = $doc-&gt;URI();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the URI (or filename) of the original document.
		    For documents obtained by parsing a string of a FH
		    without using the URI parsing argument of the corresponding <function>parse_*</function> function,
		    the result is a generated string unknown-XYZ where XYZ is some number;
		    for documents created with the constructor <function>new</function>,
		    the URI is undefined.
                    </para>
		    <para>The value can be modified by calling <function>setURI</function>
		    method on the document node.</para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>setURI</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$doc-&gt;setURI($strURI);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Sets the URI of the document reported by the method URI
		    (see also the URI argument to the various <function>parse_*</function> functions).
		    </para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>encoding</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$strEncoding = $doc-&gt;encoding();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>returns the encoding string of the document.</para>

                    <programlisting>my $doc = XML::LibXML-&gt;createDocument( "1.0", "ISO-8859-15" );
print $doc-&gt;encoding; # prints ISO-8859-15</programlisting>

                </listitem>
            </varlistentry>
            <varlistentry>
                <term>actualEncoding</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$strEncoding = $doc-&gt;actualEncoding();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>returns the encoding in which the XML will be returned by $doc-&gt;toString().
                      This is usually the original encoding of the document as declared
                      in the XML declaration and returned by $doc-&gt;encoding.
                      If the original encoding is not known (e.g. if created in memory or parsed from a
                      XML without a declared encoding), 'UTF-8' is returned.
		    </para>

                    <programlisting>my $doc = XML::LibXML-&gt;createDocument( "1.0", "ISO-8859-15" );
print $doc-&gt;encoding; # prints ISO-8859-15</programlisting>

                </listitem>
            </varlistentry>

            <varlistentry>
                <term>setEncoding</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$doc-&gt;setEncoding($new_encoding);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This method allows one to change the declaration of
                      encoding in the XML declaration of the document.
		      The value also affects the encoding in which the
		      document is serialized to XML by $doc-&gt;toString().
	              Use setEncoding() to remove the encoding declaration.
		    </para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>version</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$strVersion = $doc-&gt;version();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>returns the version string of the document</para>

                    <para><emphasis>getVersion()</emphasis> is an alternative form of this function.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>standalone</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$doc-&gt;standalone</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function returns the Numerical value of a documents XML declarations standalone attribute. It returns <emphasis>1</emphasis> if
                    standalone="yes" was found, <emphasis>0</emphasis> if standalone="no" was found and <emphasis>-1</emphasis> if standalone
                    was not specified (default on creation).</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>setStandalone</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$doc-&gt;setStandalone($numvalue);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Through this method it is possible to alter the value of a documents standalone attribute. Set it to <emphasis>1</emphasis> to set
                    standalone="yes", to <emphasis>0</emphasis> to set standalone="no" or set it to <emphasis>-1</emphasis> to remove the
                    standalone attribute from the XML declaration.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>compression</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>my $compression = $doc-&gt;compression;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>libxml2 allows reading of documents directly from gzipped files. In this case the compression variable is set to the compression level
                    of that file (0-8). If XML::LibXML parsed a different source or the file wasn't compressed, the returned value will be
                    <emphasis>-1</emphasis>.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>setCompression</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$doc-&gt;setCompression($ziplevel);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>If one intends to write the document directly to a file, it is possible to set the compression level for a given document. This level
                    can be in the range from 0 to 8. If XML::LibXML should not try to compress use <emphasis>-1</emphasis> (default).</para>

                    <para>Note that this feature will <emphasis>only</emphasis> work if libxml2 is compiled with zlib support and toFile() is used for output.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>toString</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$docstring = $dom-&gt;toString($format);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para><emphasis>toString</emphasis> is a DOM serializing function,
		    so the DOM Tree is serialized into an XML string, ready for output.</para>
                    <para>IMPORTANT: unlike toString for other nodes, on document nodes
		      this function returns the XML as a byte string in the original encoding of the
                      document (see the actualEncoding() method)! This means you
		      can simply do:
		    </para>
            <programlisting>open my $out_fh, '&gt;', $file;
print {$out_fh} $doc-&gt;toString;</programlisting>
                   <para>regardless of the actual encoding of the document.
		   See the section on encodings in <xref linkend="XML-LibXML"/> for more details.</para>
                    <para>The optional <emphasis>$format</emphasis> parameter sets the indenting of the output. This parameter is expected to be an
                    <function>integer</function> value, that specifies that indentation should be used. The format parameter can have three different values if
                    it is used:</para>

                    <para>If $format is 0, than the document is dumped as it was originally parsed</para>

                    <para>If $format is 1, libxml2 will add ignorable white spaces, so the nodes content is easier to read. Existing text nodes will not be
                    altered</para>

                    <para>If $format is 2 (or higher), libxml2 will act as $format == 1 but it add a leading and a trailing line break to each text node.</para>

                    <para>libxml2 uses a hard-coded indentation of 2 space characters per indentation level. This value can not be altered on run-time.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>toStringC14N</term>

                <listitem>
                    <para><funcsynopsis><funcsynopsisinfo>$c14nstr = $doc-&gt;toStringC14N($comment_flag, $xpath [, $xpath_context ]); </funcsynopsisinfo></funcsynopsis>
	            See the documentation in <xref linkend="XML-LibXML-Node"/>.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>toStringEC14N</term>

                <listitem>
                    <para><funcsynopsis><funcsynopsisinfo>$ec14nstr = $doc-&gt;toStringEC14N($comment_flag, $xpath [, $xpath_context ], $inclusive_prefix_list); </funcsynopsisinfo></funcsynopsis>
	            See the documentation in <xref linkend="XML-LibXML-Node"/>.
                   </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>serialize</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$str = $doc-&gt;serialize($format); </funcsynopsisinfo>
                    </funcsynopsis>

                    <para>An alias for toString(). This function was name added to be more consistent
		      with libxml2.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>serialize_c14n</term>

                <listitem>
                    <para>An alias for toStringC14N().</para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>serialize_exc_c14n</term>

                <listitem>
                    <para>An alias for toStringEC14N().</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>toFile</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$state = $doc-&gt;toFile($filename, $format);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function is similar to toString(), but it writes the document directly into a filesystem. This function is very useful, if one
                    needs to store large documents.</para>

                    <para>The format parameter has the same behaviour as in toString().</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>toFH</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$state = $doc-&gt;toFH($fh, $format);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function is similar to toString(), but it writes the document directly to a filehandle or a stream. A byte stream in the document encoding is passed to the file handle. Do NOT apply any <literal>:encoding(...)</literal> or <literal>:utf8</literal> PerlIO layer to
		    the filehandle! See the section on encodings in <xref linkend="XML-LibXML"/> for more details.</para>

                    <para>The format parameter has the same behaviour as in toString().</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>toStringHTML</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$str = $document-&gt;toStringHTML();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para><emphasis>toStringHTML</emphasis> serialize the tree to a byte string in the document encoding as HTML. With this method indenting is automatic and managed by
                    libxml2 internally.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>serialize_html</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$str = $document-&gt;serialize_html();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>An alias for toStringHTML().</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>is_valid</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$bool = $dom-&gt;is_valid();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns either TRUE or FALSE depending on whether the DOM Tree is a valid Document or not.</para>

                    <para>You may also pass in a <xref linkend="XML-LibXML-Dtd"/> object, to validate against an external DTD:</para>

                    <programlisting> if (!$dom-&gt;is_valid($dtd)) {
     warn("document is not valid!");
 }</programlisting>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>validate</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$dom-&gt;validate();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This is an exception throwing equivalent of is_valid. If the document is not valid it will throw an exception containing the error.
                    This allows you much better error reporting than simply is_valid or not.</para>

                    <para>Again, you may pass in a DTD object</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>documentElement</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$root = $dom-&gt;documentElement();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the root element of the Document. A document can have just one root element to contain the documents data.</para>

                    <para>Optionally one can use <emphasis>getDocumentElement</emphasis>.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>setDocumentElement</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$dom-&gt;setDocumentElement( $root );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function enables you to set the root element for a document. The function supports the import of a node from a different document
                    tree, but does not support a document fragment as $root.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>createElement</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$element = $dom-&gt;createElement( $nodename );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function creates a new Element Node bound to the DOM with the name <function>$nodename</function>.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>createElementNS</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$element = $dom-&gt;createElementNS( $namespaceURI, $nodename );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function creates a new Element Node bound to the DOM with the name <function>$nodename</function> and placed in the given
                    namespace.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>createTextNode</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$text = $dom-&gt;createTextNode( $content_text );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>As an equivalent of <emphasis>createElement</emphasis>, but it creates a <emphasis>Text Node</emphasis> bound to the DOM.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>createComment</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$comment = $dom-&gt;createComment( $comment_text );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>As an equivalent of <emphasis>createElement</emphasis>, but it creates a <emphasis>Comment Node</emphasis> bound to the DOM.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>createAttribute</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$attrnode = $doc-&gt;createAttribute($name [,$value]);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Creates a new Attribute node.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>createAttributeNS</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$attrnode = $doc-&gt;createAttributeNS( namespaceURI, $name [,$value] );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Creates an Attribute bound to a namespace.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>createDocumentFragment</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$fragment = $doc-&gt;createDocumentFragment();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function creates a DocumentFragment.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>createCDATASection</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$cdata = $dom-&gt;createCDATASection( $cdata_content );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Similar to createTextNode and createComment, this function creates a CDataSection bound to the current DOM.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>createProcessingInstruction</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>my $pi = $doc-&gt;createProcessingInstruction( $target, $data );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>create a processing instruction node.</para>

                    <para>Since this method is quite long one may use its short form <emphasis>createPI()</emphasis>.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>createEntityReference</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>my $entref = $doc-&gt;createEntityReference($refname);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>If a document has a DTD specified, one can create entity references by using this function. If one wants to add a entity reference to
                    the document, this reference has to be created by this function.</para>

                    <para>An entity reference is unique to a document and cannot be passed to other documents as other nodes can be passed.</para>

                    <para><emphasis>NOTE:</emphasis> A text content containing something that looks like an entity reference, will not be expanded to a real
                    entity reference unless it is a predefined entity</para>

                    <programlisting> my $string = "&amp;foo;";
 $some_element-&gt;appendText( $string );
 print $some_element-&gt;textContent; # prints "&amp;amp;foo;"</programlisting>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>createInternalSubset</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$dtd = $document-&gt;createInternalSubset( $rootnode, $public, $system);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function creates and adds an internal subset to the given document. Because the function automatically adds the DTD to the document
                    there is no need to add the created node explicitly to the document.</para>

                    <programlisting> my $document = XML::LibXML::Document-&gt;new();
 my $dtd      = $document-&gt;createInternalSubset( "foo", undef, "foo.dtd" );</programlisting>

                    <para>will result in the following XML document:</para>

                    <programlisting>&lt;?xml version="1.0"?&gt;
 &lt;!DOCTYPE foo SYSTEM "foo.dtd"&gt;                    </programlisting>

                    <para>By setting the public parameter it is possible to set PUBLIC DTDs to a given document. So</para>

                    <programlisting>my $document = XML::LibXML::Document-&gt;new();
my $dtd      = $document-&gt;createInternalSubset( "foo", "-//FOO//DTD FOO 0.1//EN", undef );
</programlisting>

                    <para>will cause the following declaration to be created on the document:</para>

                    <programlisting>&lt;?xml version="1.0"?&gt;
&lt;!DOCTYPE foo PUBLIC "-//FOO//DTD FOO 0.1//EN"&gt;</programlisting>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>createExternalSubset</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$dtd = $document-&gt;createExternalSubset( $rootnode_name, $publicId, $systemId);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function is similar to <function>createInternalSubset()</function> but this DTD is considered to be external and is therefore not
                    added to the document itself. Nevertheless it can be used for validation purposes.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>importNode</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$document-&gt;importNode( $node );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>If a node is not part of a document, it can be imported to another document. As specified in DOM Level 2 Specification the Node will
                    not be altered or removed from its original document (<function>$node-&gt;cloneNode(1)</function> will get called implicitly).</para>

                    <para><emphasis>NOTE:</emphasis> Don't try to use importNode() to import sub-trees that contain an entity reference - even if the entity
                    reference is the root node of the sub-tree. This will cause serious problems to your program. This is a limitation of libxml2 and not of
                    XML::LibXML itself.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>adoptNode</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$document-&gt;adoptNode( $node );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>If a node is not part of a document, it can be imported to another document. As specified in DOM Level 3 Specification the Node will
                    not be altered but it will removed from its original document.</para>

                    <para>After a document adopted a node, the node, its attributes and all its descendants belong to the new document. Because the node does
                    not belong to the old document, it will be unlinked from its old location first.</para>

                    <para><emphasis>NOTE:</emphasis> Don't try to adoptNode() to import sub-trees that contain entity references - even if the entity
                    reference is the root node of the sub-tree. This will cause serious problems to your program. This is a limitation of libxml2 and not of
                    XML::LibXML itself.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>externalSubset</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>my $dtd = $doc-&gt;externalSubset;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>If a document has an external subset defined it will be returned by this function.</para>

                    <para><emphasis>NOTE</emphasis> Dtd nodes are no ordinary nodes in libxml2. The support for these nodes in XML::LibXML is still limited. In
                    particular one may not want use common node function on doctype declaration nodes!</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>internalSubset</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>my $dtd = $doc-&gt;internalSubset;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>If a document has an internal subset defined it will be returned by this function.</para>

                    <para><emphasis>NOTE</emphasis> Dtd nodes are no ordinary nodes in libxml2. The support for these nodes in XML::LibXML is still limited. In
                    particular one may not want use common node function on doctype declaration nodes!</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>setExternalSubset</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$doc-&gt;setExternalSubset($dtd);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para><emphasis>EXPERIMENTAL!</emphasis></para>

                    <para>This method sets a DTD node as an external subset of the given document.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>setInternalSubset</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$doc-&gt;setInternalSubset($dtd);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para><emphasis>EXPERIMENTAL!</emphasis></para>

                    <para>This method sets a DTD node as an internal subset of the given document.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>removeExternalSubset</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>my $dtd = $doc-&gt;removeExternalSubset();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para><emphasis>EXPERIMENTAL!</emphasis></para>

                    <para>If a document has an external subset defined it can be removed from the document by using this function. The removed dtd node will be
                    returned.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>removeInternalSubset</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>my $dtd = $doc-&gt;removeInternalSubset();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para><emphasis>EXPERIMENTAL!</emphasis></para>

                    <para>If a document has an internal subset defined it can be removed from the document by using this function. The removed dtd node will be
                    returned.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>getElementsByTagName</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>my @nodelist = $doc-&gt;getElementsByTagName($tagname);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Implements the DOM Level 2 function</para>

                    <para>In SCALAR context this function returns an <olink targetdoc="XML::LibXML::NodeList">XML::LibXML::NodeList</olink> object.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>getElementsByTagNameNS</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>my @nodelist = $doc-&gt;getElementsByTagNameNS($nsURI,$tagname);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Implements the DOM Level 2 function</para>

                    <para>In SCALAR context this function returns an <olink targetdoc="XML::LibXML::NodeList">XML::LibXML::NodeList</olink> object.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>getElementsByLocalName</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>my @nodelist = $doc-&gt;getElementsByLocalName($localname);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This allows the fetching of all nodes from a given document with the given Localname.</para>

                    <para>In SCALAR context this function returns an <olink targetdoc="XML::LibXML::NodeList">XML::LibXML::NodeList</olink> object.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>getElementById</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>my $node = $doc-&gt;getElementById($id);</funcsynopsisinfo>
                    </funcsynopsis>
                    <para>Returns the element that has an ID attribute
		      with the given value. If no such element exists,
		      this returns undef.</para>
		    <para>Note: the ID of an element
		      may change while manipulating the document.
                      For documents with a DTD, the information about ID attributes
                      is only available if DTD loading/validation has been requested.
                      For HTML documents parsed with the HTML
		      parser ID detection is done
		      automatically. In XML documents, all "xml:id"
		      attributes are considered to be of type ID.
                      You can test ID-ness of an attribute node
                      with $attr-&gt;isId().
		    </para>
		    <para>In versions 1.59 and earlier this method was
		      called getElementsById() (plural) by
		      mistake. Starting from 1.60 this name is
		      maintained as an alias only for backward compatibility.
		    </para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>indexElements</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$dom-&gt;indexElements();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function causes libxml2 to stamp all elements in a document with their document position index which considerably speeds up XPath
                    queries for large documents. It should only be used with static documents that won't be further changed by any DOM methods, because once
                    a document is indexed, XPath will always prefer the index to other methods of determining the document order of nodes. XPath could therefore
                    return improperly ordered node-lists when applied on a document that has been changed after being indexed. It is of course possible to use
                    this method to re-index a modified document before using it with XPath again. This function is not a part of the DOM specification.</para>

                    <para>This function returns number of elements indexed, -1 if error occurred, or -2 if this feature is not available in the running libxml2.</para>
                </listitem>
            </varlistentry>
        </variablelist>
      </sect1>
    </chapter>

    <chapter id="XML-LibXML-Node">
        <title>Abstract Base Class of XML::LibXML Nodes</title>

        <titleabbrev>XML::LibXML::Node</titleabbrev>
        <sect1>
            <title>Synopsis</title>
            <programlisting>use XML::LibXML;</programlisting>
        </sect1>
        <sect1>
            <title>Description</title>

        <para>XML::LibXML::Node defines functions that are common to
        all Node Types. An XML::LibXML::Node should never be created
        standalone, but as an instance of a high level class such as
        XML::LibXML::Element or XML::LibXML::Text. The class itself should
        provide only common functionality. In XML::LibXML each node is
        part either of a document or a document-fragment. Because of
        this there is no node without a parent. This may causes
        confusion with "unbound" nodes.</para>
	</sect1>
        <sect1>
            <title>Methods</title>
		    <para>
	      Many functions listed here are
	      extensively documented in the <ulink url="http://www.w3.org/TR/DOM-Level-3-Core/">DOM Level 3 specification</ulink>. Please refer to
	      the specification for extensive documentation.
	    </para>

        <variablelist>
            <varlistentry>
                <term>nodeName</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$name = $node-&gt;nodeName;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the node's name. This function is
	              aware of namespaces and returns the full name of
                      the current node (<function>prefix:localname</function>).
	            </para>
                    <para>Since 1.62 this function also returns the correct
	              DOM names for node types with constant names, namely:
                      #text, #cdata-section, #comment, #document,
	              #document-fragment.
	            </para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>setNodeName</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;setNodeName( $newName );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>In very limited situations, it is useful to change a nodes name. In the DOM specification this should throw an error. This Function is
                    aware of namespaces.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>isSameNode</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$bool = $node-&gt;isSameNode( $other_node );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>returns TRUE (1) if the given nodes refer to
                    the same node structure, otherwise FALSE (0) is
                    returned.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>isEqual</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$bool = $node-&gt;isEqual( $other_node );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>deprecated version of isSameNode().</para>

                    <para><emphasis>NOTE</emphasis> isEqual will change behaviour to follow the DOM specification</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>unique_key</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$num = $node-&gt;unique_key;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function is not specified for any DOM level. It returns a key guaranteed to be unique for this node, and to always be the same value for this node. In other words, two node objects return the same key if and only if isSameNode indicates that they are the same node.</para>

                    <para>The returned key value is useful as a key in hashes.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>nodeValue</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$content = $node-&gt;nodeValue;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>If the node has any content (such as stored in a <function>text node</function>) it can get requested through this function.</para>

                    <para><emphasis>NOTE:</emphasis> Element Nodes have no content per definition. To get the text value of an Element use textContent()
                    instead!</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>textContent</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$content = $node-&gt;textContent;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>this function returns the content of all text nodes in the descendants of the given node as specified in DOM.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>nodeType</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$type = $node-&gt;nodeType;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Return a numeric value representing the node type of this node.
		    The module XML::LibXML by default exports constants
		    for the node types (see the EXPORT section in the
		    <xref linkend="XML-LibXML"/> manual page).</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>unbindNode</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;unbindNode();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Unbinds the Node from its siblings and Parent, but not from the Document it belongs to. If the node is not inserted into the DOM
                    afterwards, it will be lost after the program terminates. From a low level view, the unbound node is stripped from the context it is and
                    inserted into a (hidden) document-fragment.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>removeChild</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$childnode = $node-&gt;removeChild( $childnode );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This will unbind the Child Node from its parent <function>$node</function>. The function returns the unbound node. If
                    <function>oldNode</function> is not a child of the given Node the function will fail.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>replaceChild</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$oldnode = $node-&gt;replaceChild( $newNode, $oldNode );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Replaces the <function>$oldNode</function> with the <function>$newNode</function>. The <function>$oldNode</function> will be unbound
                    from the Node. This function differs from the DOM L2 specification, in the case, if the new node is not part of the document, the node will
                    be imported first.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>replaceNode</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;replaceNode($newNode);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function is very similar to replaceChild(), but it replaces the node itself rather than a childnode. This is useful if a node
                    found by any XPath function, should be replaced.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>appendChild</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$childnode = $node-&gt;appendChild( $childnode );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The function will add the <function>$childnode</function> to the end of <function>$node</function>'s children. The function should
                    fail, if the new childnode is already a child of <function>$node</function>. This function differs from the DOM L2 specification, in the
                    case, if the new node is not part of the document, the node will be imported first.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>addChild</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$childnode = $node-&gt;addChild( $childnode );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>As an alternative to appendChild() one can use the addChild() function. This function is a bit faster, because it avoids all DOM
                    conformity checks. Therefore this function is quite useful if one builds XML documents in memory where the order and ownership (<function>ownerDocument</function>)
                    is assured.</para>

                    <para>addChild() uses libxml2's own xmlAddChild() function. Thus it has to be used with extra care: If a text node is added to a node
                    and the node itself or its last childnode is as well a text node, the node to add will be merged with the one already available. The current
                    node will be removed from memory after this action. Because perl is not aware of this action, the perl instance is still available.
                    XML::LibXML will catch the loss of a node and refuse to run any function called on that node.</para>

                    <programlisting> my $t1 = $doc-&gt;createTextNode( "foo" );
 my $t2 = $doc-&gt;createTextNode( "bar" );
 $t1-&gt;addChild( $t2 );       # is OK
 my $val = $t2-&gt;nodeValue(); # will fail, script dies</programlisting>

                    <para>Also addChild() will not check if the added node belongs to the same document as the node it will be added to. This could lead to
                    inconsistent documents and in more worse cases even to memory violations, if one does not keep track of this issue.</para>

                    <para>Although this sounds like a lot of trouble, addChild() is useful if a document is built from a stream, such as happens sometimes in
                    SAX handlers or filters.</para>

                    <para>If you are not sure about the source of your nodes, you better stay with appendChild(), because this function is more user friendly in
                    the sense of being more error tolerant.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>addNewChild</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node = $parent-&gt;addNewChild( $nsURI, $name );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Similar to <function>addChild()</function>, this function uses low level libxml2 functionality to provide faster interface for DOM
                    building. <emphasis>addNewChild()</emphasis> uses <function>xmlNewChild()</function> to create a new node on a given parent element.</para>

                    <para>addNewChild() has two parameters $nsURI and $name, where $nsURI is an (optional) namespace URI. $name is the fully qualified element
                    name; addNewChild() will determine the correct prefix if necessary.</para>

                    <para>The function returns the newly created node.</para>

                    <para>This function is very useful for DOM building, where a created node can be directly associated with its parent. <emphasis>NOTE</emphasis>
                    this function is not part of the DOM specification and its use will limit your code to XML::LibXML.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>addSibling</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;addSibling($newNode);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>addSibling() allows adding an additional node to the end of a nodelist, defined by the given node.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>cloneNode</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$newnode =$node-&gt;cloneNode( $deep );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para><emphasis>cloneNode</emphasis> creates a
                    copy of <function>$node</function>. When $deep is
                    set to 1 (true) the function will copy all
                    child nodes as well. If $deep is 0 only the current
                    node will be copied. Note that in case of element,
                    attributes are copied even if $deep is 0.
                    </para>
                    <para>Note that the behavior of this function for $deep=0
	              has changed in 1.62 in order to be consistent with the DOM spec
                      (in older versions attributes and namespace information
                      was not copied for elements).</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>parentNode</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$parentnode = $node-&gt;parentNode;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns simply the Parent Node of the current node.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>nextSibling</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$nextnode = $node-&gt;nextSibling();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the next sibling if any .</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>nextNonBlankSibling</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$nextnode = $node-&gt;nextNonBlankSibling();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the next non-blank sibling if any (a node is blank if it is a Text or CDATA node consisting of whitespace only). This method is not defined by DOM.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>previousSibling</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$prevnode = $node-&gt;previousSibling();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Analogous to <emphasis>getNextSibling</emphasis> the function returns the previous sibling if any.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>previousNonBlankSibling</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$prevnode = $node-&gt;previousNonBlankSibling();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the previous non-blank sibling if any (a node is blank if it is a Text or CDATA node consisting of whitespace only). This method is not defined by DOM.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>hasChildNodes</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$boolean = $node-&gt;hasChildNodes();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>If the current node has child nodes this function returns TRUE (1), otherwise it returns FALSE (0, not undef).</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>firstChild</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$childnode = $node-&gt;firstChild;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>If a node has child nodes this function will return the first node in the child list.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>lastChild</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$childnode = $node-&gt;lastChild;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>If the <function>$node</function> has child nodes this function returns the last child node.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>ownerDocument</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$documentnode = $node-&gt;ownerDocument;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Through this function it is always possible to access the document the current node is bound to.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>getOwner</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node = $node-&gt;getOwner;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function returns the node the current node is associated with. In most cases this will be a document node or a document fragment
                    node.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>setOwnerDocument</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;setOwnerDocument( $doc );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function binds a node to another DOM. This method unbinds the node first, if it is already bound to another document.</para>

                    <para>This function is the opposite calling of <xref linkend="XML-LibXML-Document"/>'s adoptNode() function. Because of this it has the same limitations
                    with Entity References as adoptNode().</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>insertBefore</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;insertBefore( $newNode, $refNode );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The method inserts <function>$newNode</function> before <function>$refNode</function>. If <function>$refNode</function> is undefined,
                    the newNode will be set as the new last child of the parent node. This function differs from the DOM L2 specification, in the case, if the
                    new node is not part of the document, the node will be imported first, automatically.</para>

                    <para>$refNode has to be passed to the function even if it is undefined:</para>

                    <programlisting> $node-&gt;insertBefore( $newNode, undef ); # the same as $node-&gt;appendChild( $newNode );
 $node-&gt;insertBefore( $newNode ); # wrong</programlisting>

                    <para>Note, that the reference node has to be a direct child of the node the function is called on. Also, $newChild is not allowed to be an
                    ancestor of the new parent node.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>insertAfter</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;insertAfter( $newNode, $refNode );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The method inserts <function>$newNode</function> after <function>$refNode</function>. If <function>$refNode</function> is undefined,
                    the newNode will be set as the new last child of the parent node.</para>

                    <para>Note, that $refNode has to be passed explicitly even if it is undef.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>findnodes</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>@nodes = $node-&gt;findnodes( $xpath_expression );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para><emphasis>findnodes</emphasis> evaluates the xpath expression (XPath 1.0) on the current node and returns the resulting node set as an array. In scalar context, returns an <olink targetdoc="XML::LibXML::NodeList">XML::LibXML::NodeList</olink> object.</para>
          <para>The xpath expression can be passed either as a string, or
	  as a  <olink targetdoc="XML::LibXML::XPathExpression">XML::LibXML::XPathExpression</olink> object.
	  </para>
	  <para><emphasis>NOTE ON NAMESPACES AND XPATH</emphasis>:</para>
	  <para>A common mistake about
	    XPath is to assume that node tests consisting of an
	    element name with no prefix match elements in the default
	    namespace. This assumption is wrong - by XPath
	    specification, such node tests can only match elements
	    that are in no (i.e. null) namespace.
	  </para>
	  <para>
	    So, for example, one cannot match the root element of an
	    XHTML document with <literal>$node-&gt;find('/html')</literal>
	    since <literal>'/html'</literal> would only match if the
	    root element <literal>&lt;html&gt;</literal> had no
	    namespace, but all XHTML elements belong to the namespace
	    http://www.w3.org/1999/xhtml. (Note that
	    <literal>xmlns="..."</literal> namespace declarations can
	    also be specified in a DTD, which makes the situation even worse, since
	    the XML document looks as if there was no default namespace).
	  </para>
          <para>There are several possible ways to deal with namespaces in XPath:
	  </para>
	  <itemizedlist>
	    <listitem>
	      <para>
		The recommended way is to use the
		<xref linkend="XML-LibXML-XPathContext"/> module
		to define an explicit context
		for XPath evaluation, in which a document independent
		prefix-to-namespace mapping can be defined. For
		example:
	      </para>
	      <programlisting>my $xpc = XML::LibXML::XPathContext-&gt;new;
$xpc-&gt;registerNs('x', 'http://www.w3.org/1999/xhtml');
$xpc-&gt;find('/x:html',$node);</programlisting>
	    </listitem>
	    <listitem><para>
		Another possibility is to use prefixes declared
		in the queried document (if known).
		If the document declares a prefix for the
		namespace in question (and the context node is in the
		scope of the declaration),
		<function>XML::LibXML</function> allows you to use the
		prefix in the XPath expression, e.g.:
	      </para>
	      <programlisting>$node-&gt;find('/x:html');</programlisting>
	    </listitem>
	  </itemizedlist>
	  <para>See also XML::LibXML::XPathContext-&gt;findnodes.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>find</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$result = $node-&gt;find( $xpath );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para><emphasis>find</emphasis> evaluates the XPath 1.0 expression using the current node as the context of the expression, and returns the
                    result depending on what type of result the XPath expression had. For example, the XPath "1 * 3 + 52" results in a
                    <olink targetdoc="XML::LibXML::Number">XML::LibXML::Number</olink> object being returned. Other expressions might return an <olink targetdoc="XML::LibXML::Boolean">XML::LibXML::Boolean</olink>
                    object, or an <olink targetdoc="XML::LibXML::Literal">XML::LibXML::Literal</olink> object (a string). Each of those objects uses Perl's overload feature to "do
                    the right thing" in different contexts.</para>
          <para>The xpath expression can be passed either as a string,
	  or as a  <olink targetdoc="XML::LibXML::XPathExpression">XML::LibXML::XPathExpression</olink> object.
	  </para>
	  <para>See also <xref linkend="XML-LibXML-XPathContext"/>-&gt;find.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>findvalue</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>print $node-&gt;findvalue( $xpath );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para><emphasis>findvalue</emphasis> is exactly equivalent to:</para>

                    <programlisting> $node-&gt;find( $xpath )-&gt;to_literal;              </programlisting>

                    <para>That is, it returns the literal value of the results. This enables you to ensure that you get a string back from your search, allowing
                    certain shortcuts. This could be used as the equivalent of XSLT's &lt;xsl:value-of select="some_xpath"/&gt;.</para>
	  <para>See also <xref linkend="XML-LibXML-XPathContext"/>-&gt;findvalue.</para>
          <para>The xpath expression can be passed either as a string, or
	  as a  <olink targetdoc="XML::LibXML::XPathExpression">XML::LibXML::XPathExpression</olink> object.
	  </para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>exists</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$bool = $node-&gt;exists( $xpath_expression );</funcsynopsisinfo>
                    </funcsynopsis>
		    <para>This method behaves like <emphasis>findnodes</emphasis>, except
		    that it only returns a boolean value (1 if the expression matches a node, 0 otherwise)
		    and may be faster than <emphasis>findnodes</emphasis>, because
		    the XPath evaluation may stop early on the first match (this is true for libxml2 >= 2.6.27).
		    </para><para>For XPath expressions that do not return node-set,
		    the method returns true if the returned value is a non-zero number or a non-empty string.</para>
		</listitem>
	    </varlistentry>

            <varlistentry>
                <term>childNodes</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>@childnodes = $node-&gt;childNodes();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para><emphasis>childNodes</emphasis> implements a more intuitive interface to the childnodes of the current node. It enables you to pass
                    all children directly to a <function>map</function> or <function>grep</function>. If this function is called in scalar context, a
                    <olink targetdoc="XML::LibXML::NodeList">XML::LibXML::NodeList</olink> object will be returned.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>nonBlankChildNodes</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>@childnodes = $node-&gt;nonBlankChildNodes();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This is like <emphasis>childNodes</emphasis>,
		      but returns only non-blank nodes
		      (where a node is blank if it is a Text or CDATA node consisting of whitespace only). This method is not defined by DOM.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>toString</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$xmlstring = $node-&gt;toString($format,$docencoding);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This method is similar to the method <function>toString</function> of a <xref linkend="XML-LibXML-Document"/> but for a single node. It returns a string consisting of XML serialization of the given node and all its descendants. Unlike <function>XML::LibXML::Document::toString</function>, in this case the resulting string is by default a character string (UTF-8 encoded with UTF8 flag on). An optional flag $format controls indentation, as in <function>XML::LibXML::Document::toString</function>. If the second optional $docencoding flag is true, the result will be a byte string in the document encoding (see <function>XML::LibXML::Document::actualEncoding</function>).</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>toStringC14N</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$c14nstring = $node-&gt;toStringC14N();
$c14nstring = $node-&gt;toStringC14N($with_comments, $xpath_expression , $xpath_context);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The function is similar to
                    toString(). Instead of simply serializing the
                    document tree, it transforms it as it is specified
                    in the XML-C14N Specification
                    (see <ulink url="http://www.w3.org/TR/xml-c14n">http://www.w3.org/TR/xml-c14n</ulink>).
                    Such transformation is known as
                    canonization.</para>

                    <para>If $with_comments is 0 or not defined, the
                    result-document will not contain any comments that
                    exist in the original document. To include
                    comments into the canonized document,
                    $with_comments has to be set to 1.</para>

                    <para>The parameter $xpath_expression defines the
                    nodeset of nodes that should be visible in the
                    resulting document. This can be used to filter out
                    some nodes. One has to note, that only the nodes
                    that are part of the nodeset, will be included
                    into the result-document. Their child-nodes will
                    not exist in the resulting document, unless they
                    are part of the nodeset defined by the xpath
                    expression.
		    </para>
                    <para>If $xpath_expression is omitted or empty,
                    toStringC14N() will include all nodes in the given
                    sub-tree, using the following XPath expressions:
		    with comments
		    <programlisting>(. | .//node() | .//@* | .//namespace::*)</programlisting>
		    and without comments
		    <programlisting>(. | .//node() | .//@* | .//namespace::*)[not(self::comment())]</programlisting>
		    </para>
		    <para>
		      An optional parameter $xpath_context can be used
		      to pass an <xref linkend="XML-LibXML-XPathContext"/> object defining
		      the context for evaluation of $xpath_expression.
		      This is useful for mapping namespace prefixes used in the XPath expression
		      to namespace URIs.
		      Note, however, that
		      $node will be used as the context node for the evaluation, not
		      the context node of $xpath_context!
		    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>toStringC14N_v1_1</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$c14nstring = $node-&gt;toStringC14N_v1_1();
$c14nstring = $node-&gt;toStringC14N_v1_1($with_comments, $xpath_expression , $xpath_context);</funcsynopsisinfo>
                    </funcsynopsis>
                    <para>
                        This function behaves like toStringC14N() except that
                        it uses the "XML_C14N_1_1" constant for
                        canonicalising using the "C14N 1.1 spec".
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>toStringEC14N</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$ec14nstring = $node-&gt;toStringEC14N();
$ec14nstring = $node-&gt;toStringEC14N($with_comments, $xpath_expression, $inclusive_prefix_list);
$ec14nstring = $node-&gt;toStringEC14N($with_comments, $xpath_expression, $xpath_context, $inclusive_prefix_list);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The function is similar to toStringC14N() but follows
                    the XML-EXC-C14N Specification (see <ulink url="http://www.w3.org/TR/xml-exc-c14n">http://www.w3.org/TR/xml-exc-c14n</ulink>)
	            for exclusive canonization of XML.</para>

                    <para>The arguments $with_comments, $xpath_expression, $xpath_context are as in toStringC14N().
		    An ARRAY reference can be passed as the last argument $inclusive_prefix_list,
		    listing namespace prefixes that are to be handled in the manner described by the Canonical XML Recommendation (i.e. preserved in the output even if the namespace is not used). C.f. the spec for details.
	            </para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>serialize</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$str = $doc-&gt;serialize($format); </funcsynopsisinfo>
                    </funcsynopsis>
                    <para>An alias for toString(). This function was name added to be more consistent
		      with libxml2.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>serialize_c14n</term>

                <listitem>
                    <para>An alias for toStringC14N().</para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>serialize_exc_c14n</term>

                <listitem>
                    <para>An alias for toStringEC14N().</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>localname</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$localname = $node-&gt;localname;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the local name of a tag. This is the part behind the colon.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>prefix</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$nameprefix = $node-&gt;prefix;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the prefix of a tag. This is the part before the colon.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>namespaceURI</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$uri = $node-&gt;namespaceURI();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>returns the URI of the current namespace.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>hasAttributes</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$boolean = $node-&gt;hasAttributes();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>returns 1 (TRUE) if the current node has any attributes set, otherwise 0 (FALSE) is returned.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>attributes</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>@attributelist = $node-&gt;attributes();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function returns all attributes and namespace declarations assigned to the given node.</para>

                    <para>Because XML::LibXML does not implement namespace declarations and attributes the same way, it is required to test what kind of node is
                    handled while accessing the functions result.</para>

                    <para>If this function is called in array context the attribute nodes are returned as an array. In scalar context, the function will return a
                    <olink targetdoc="XML::LibXML::NamedNodeMap">XML::LibXML::NamedNodeMap</olink> object.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>lookupNamespaceURI</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$URI = $node-&gt;lookupNamespaceURI( $prefix );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Find a namespace URI by its prefix starting at the current node.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>lookupNamespacePrefix</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$prefix = $node-&gt;lookupNamespacePrefix( $URI );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Find a namespace prefix by its URI starting at the current node.</para>

                    <para><emphasis>NOTE</emphasis> Only the namespace URIs are meant to be unique. The prefix is only document related. Also the document might
                    have more than a single prefix defined for a namespace.</para>
                </listitem>
            </varlistentry>


            <varlistentry>
                <term>normalize</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;normalize;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function normalizes adjacent text nodes. This function is not as strict as libxml2's xmlTextMerge() function, since it will
                    not free a node that is still referenced by the perl layer.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>getNamespaces</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>@nslist = $node-&gt;getNamespaces;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>If a node has any namespaces defined, this function will return these namespaces. Note, that this will not return all namespaces that
                    are in scope, but only the ones declared explicitly for that node.</para>

                    <para>Although getNamespaces is available for all nodes, it only makes sense if used with element nodes.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>removeChildNodes</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;removeChildNodes();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function is not specified for any DOM level: It removes all childnodes from a node in a single step. Other than the libxml2
                    function itself (xmlFreeNodeList), this function will not immediately remove the nodes from the memory. This saves one from getting memory
                    violations, if there are nodes still referred to from the Perl level.</para>
                </listitem>
            </varlistentry>

        <varlistentry>
          <term>baseURI ()</term>
          <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$strURI = $node-&gt;baseURI();</funcsynopsisinfo>
                    </funcsynopsis>
            <para>
	    Searches for the base URL of the node. The method should work on both XML
 and HTML documents even if base mechanisms for these are completely different.
 It returns the base as defined in RFC 2396 sections
 "5.1.1. Base URI within Document Content"
 and
 "5.1.2. Base URI from the Encapsulating Entity".
 However it does not return the document base (5.1.3), use method <function>URI</function>
	      of <function>XML::LibXML::Document</function> for this.
	    </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>setBaseURI ($strURI)</term>
          <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;setBaseURI($strURI);</funcsynopsisinfo>
                    </funcsynopsis>
            <para>This method only does something useful for an element node
	    in an XML document.
            It sets the xml:base attribute on the node to $strURI, which
	    effectively sets the base URI of the node to the same value.
	    </para>
	    <para>
	    Note: For HTML documents this behaves as if the document was XML
	    which may not be desired, since it does not effectively
	    set the base URI of the node. See RFC 2396 appendix D
	    for an example of how base URI can be specified in HTML.
	    </para>
          </listitem>
        </varlistentry>

            <varlistentry>
                <term>nodePath</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;nodePath();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function is not specified for any DOM level: It returns a canonical structure based XPath for a given node.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>line_number</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$lineno = $node-&gt;line_number();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function returns the line number where the tag was found during parsing. If a node is added to the document the line number is 0.
                    Problems may occur, if a node from one document is passed to another one.</para>
		    <para>IMPORTANT:
		    Due to limitations in the libxml2 library line numbers greater than
		    65535 will be returned as 65535. Please see
		    <ulink url="http://bugzilla.gnome.org/show_bug.cgi?id=325533">http://bugzilla.gnome.org/show_bug.cgi?id=325533</ulink> for more details.
		    </para>
                    <para>Note: line_number() is special to XML::LibXML and not part of the DOM specification.</para>

                    <para>If the line_numbers flag of the parser was not activated before parsing, line_number() will always return 0.</para>
                </listitem>
            </varlistentry>
        </variablelist>
      </sect1>
    </chapter>

    <chapter id="XML-LibXML-Element">
        <title>XML::LibXML Class for Element Nodes</title>

        <titleabbrev>XML::LibXML::Element</titleabbrev>
        <sect1>
            <title>Synopsis</title>
            <programlisting>use XML::LibXML;
# Only methods specific to Element nodes are listed here,
# see the XML::LibXML::Node manpage for other methods</programlisting>
        </sect1>
	<sect1>
	  <title>Methods</title>
	  <para>
	    The class inherits from <xref linkend="XML-LibXML-Node"/>.
	    The documentation for Inherited methods is not listed here.
	  </para>
	  <para>
	    Many functions listed here are
	    extensively documented in the <ulink url="http://www.w3.org/TR/DOM-Level-3-Core/">DOM Level 3 specification</ulink>. Please refer to
	    the specification for extensive documentation.
	  </para>
	  <variablelist>
            <varlistentry>
                <term>new</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node = XML::LibXML::Element-&gt;new( $name );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function creates a new node unbound to any DOM.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>setAttribute</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;setAttribute( $aname, $avalue );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This method sets or replaces the node's attribute <function>$aname</function> to the value <function>$avalue</function></para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>setAttributeNS</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;setAttributeNS( $nsURI, $aname, $avalue );</funcsynopsisinfo>
                    </funcsynopsis>
                    <para>Namespace-aware version of <function>setAttribute</function>, where
                       <function>$nsURI</function> is a namespace URI,
	               <function>$aname</function> is a qualified name,
                       and <function>$avalue</function> is the value.
                       The namespace URI may be null (empty or undefined)
                       in order to create an attribute which has no namespace.
	            </para>
	            <para>
	               The current implementation differs from DOM in the following aspects
                    </para>
	            <para>
                       If an attribute with the same local name and namespace URI already exists
                       on the element, but its prefix differs from the prefix of <function>$aname</function>,
                       then this function is supposed to change the prefix (regardless
                       of namespace declarations and possible collisions).
                       However, the current implementation does rather the opposite.
                       If a prefix is declared for the namespace URI in the scope
                       of the attribute, then the already declared prefix is used,
	               disregarding the prefix specified in <function>$aname</function>.
                       If no prefix is declared for the namespace, the function tries
                       to declare the prefix specified in <function>$aname</function>
                       and dies if the prefix is already taken by some other namespace.
	            </para>
                    <para>According to DOM Level 2 specification, this method can also be used to
	              create or modify special attributes used for declaring XML namespaces
	              (which belong to the namespace "http://www.w3.org/2000/xmlns/" and
	              have prefix or name "xmlns"). This should work since version 1.61,
	              but again the implementation differs from DOM specification in the following:
                      if a declaration of the same namespace prefix already exists
                      on the element, then changing its value via this method
                      automatically changes the namespace of all elements and attributes
                      in its scope. This is because in libxml2 the namespace URI of an element
                      is not static but is computed from a pointer to a namespace declaration attribute.
                    </para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>getAttribute</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$avalue = $node-&gt;getAttribute( $aname );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>If <function>$node</function> has an attribute with the name <function>$aname</function>, the value of this attribute will get
                    returned.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>getAttributeNS</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$avalue = $node-&gt;getAttributeNS( $nsURI, $aname );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Retrieves an attribute value by local name and namespace URI.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>getAttributeNode</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$attrnode = $node-&gt;getAttributeNode( $aname );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Retrieve an attribute node by name. If no attribute with a given name exists, <function>undef</function> is returned.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>getAttributeNodeNS</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$attrnode = $node-&gt;getAttributeNodeNS( $namespaceURI, $aname );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Retrieves an attribute node by local name and namespace URI. If no attribute with a given localname and namespace exists, <function>undef</function> is returned.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>removeAttribute</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;removeAttribute( $aname );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The method removes the attribute <function>$aname</function> from the node's attribute list, if the attribute can be found.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>removeAttributeNS</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;removeAttributeNS( $nsURI, $aname );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Namespace version of <function>removeAttribute</function></para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>hasAttribute</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$boolean = $node-&gt;hasAttribute( $aname );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function tests if the named attribute is set for the node. If the attribute is specified, TRUE (1) will be returned, otherwise the
                    return value is FALSE (0).</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>hasAttributeNS</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$boolean = $node-&gt;hasAttributeNS( $nsURI, $aname );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>namespace version of <function>hasAttribute</function></para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>getChildrenByTagName</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>@nodes = $node-&gt;getChildrenByTagName($tagname);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The function gives direct access to all child elements of the current node with a given tagname, where
	    tagname is a qualified name, that is, in case of namespace usage it may consist of a prefix and local
	    name. This function makes things a lot easier if one needs
                    to handle big data sets. A special tagname '*' can be used to match any name.</para>

                    <para>If this function is called in SCALAR context, it returns the number of elements found.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>getChildrenByTagNameNS</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>@nodes = $node-&gt;getChildrenByTagNameNS($nsURI,$tagname);</funcsynopsisinfo>
                    </funcsynopsis>

	  <para>Namespace version of <function>getChildrenByTagName</function>. A special nsURI '*' matches any namespace URI,
	    in which case the function behaves just like <function>getChildrenByLocalName</function>.</para>

                    <para>If this function is called in SCALAR context, it returns the number of elements found.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>getChildrenByLocalName</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>@nodes = $node-&gt;getChildrenByLocalName($localname);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The function gives direct access to all child elements of the current node with a given local name. It makes things a lot easier if one needs
	    to handle big data sets. A special <function>localname</function> '*' can be used to match any local name.</para>

                    <para>If this function is called in SCALAR context, it returns the number of elements found.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>getElementsByTagName</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>@nodes = $node-&gt;getElementsByTagName($tagname);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function is part of the spec. It
	    fetches all descendants of a node with a given tagname,
	    where <function>tagname</function> is a qualified name,
	    that is, in case of namespace usage it may consist of a prefix and
	    local name.
	    A special <function>tagname</function> '*' can be used to match any tag name.
	  </para>

                    <para>In SCALAR context this function returns an <olink targetdoc="XML::LibXML::NodeList">XML::LibXML::NodeList</olink> object.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>getElementsByTagNameNS</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>@nodes = $node-&gt;getElementsByTagNameNS($nsURI,$localname);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Namespace version of <function>getElementsByTagName</function> as found in the DOM spec.
               	    A special <function>localname</function> '*' can be used to match any local name
	            and <function>nsURI</function> '*' can be used to match any namespace URI.</para>

                    <para>In SCALAR context this function returns an <olink targetdoc="XML::LibXML::NodeList">XML::LibXML::NodeList</olink> object.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>getElementsByLocalName</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>@nodes = $node-&gt;getElementsByLocalName($localname);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function is not found in the DOM specification. It is a mix of getElementsByTagName and getElementsByTagNameNS. It will fetch all
                    tags matching the given local-name. This allows one to select tags with the same local name across namespace borders.</para>

                    <para>In SCALAR context this function returns an <olink targetdoc="XML::LibXML::NodeList">XML::LibXML::NodeList</olink> object.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>appendWellBalancedChunk</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;appendWellBalancedChunk( $chunk );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Sometimes it is necessary to append a string coded XML Tree to a node. <emphasis>appendWellBalancedChunk</emphasis> will do the trick
                    for you. But this is only done if the String is <function>well-balanced</function>.</para>

                    <para><emphasis>Note that appendWellBalancedChunk() is only left for compatibility reasons</emphasis>. Implicitly it uses</para>

                    <programlisting> my $fragment = $parser-&gt;parse_balanced_chunk( $chunk );
 $node-&gt;appendChild( $fragment );</programlisting>

                    <para>This form is more explicit and makes it easier to control the flow of a script.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>appendText</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;appendText( $PCDATA );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>alias for appendTextNode().</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>appendTextNode</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;appendTextNode( $PCDATA );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This wrapper function lets you add a string directly to an element node.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>appendTextChild</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;appendTextChild( $childname , $PCDATA );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Somewhat similar with <function>appendTextNode</function>: It lets you set an Element, that contains only a <function>text node</function>
                    directly by specifying the name and the text content.</para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>setNamespace</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;setNamespace( $nsURI , $nsPrefix, $activate );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>setNamespace() allows one to apply a
                    namespace to an element. The function takes three
                    parameters: 1. the namespace URI, which is
                    required and the two optional values prefix, which
                    is the namespace prefix, as it should be used in
                    child elements or attributes as well as the
                    additional activate parameter. If prefix is not given,
                    undefined or empty, this function tries to create a
                    declaration of the default namespace.
                    </para>
                    <para>The activate parameter is most useful: If
                    this parameter is set to FALSE (0), a new namespace
                    declaration is simply added to the element
                    while the element's namespace itself is not
                    altered. Nevertheless, activate is set to TRUE (1)
                    on default. In this case the namespace
                    is used as the node's effective
                    namespace. This means the namespace prefix is
                    added to the node name and if there was a
                    namespace already active for the node, it will
                    be replaced (but its declaration is not removed from the document).
                    A new namespace declaration is only created if necessary
                    (that is, if the element is already in the scope
                    of a namespace declaration associating the prefix
                    with the namespace URI, then this declaration is reused).
	            </para>

                    <para>The following example may clarify this:</para>

                    <programlisting> my $e1 = $doc-&gt;createElement("bar");
 $e1-&gt;setNamespace("http://foobar.org", "foo")</programlisting>

                    <para>results</para>

                    <programlisting> &lt;foo:bar xmlns:foo="http://foobar.org"/&gt;</programlisting>

                    <para>while</para>

                    <programlisting> my $e2 = $doc-&gt;createElement("bar");
 $e2-&gt;setNamespace("http://foobar.org", "foo",0)</programlisting>

                    <para>results only</para>

                    <programlisting> &lt;bar xmlns:foo="http://foobar.org"/&gt;</programlisting>

                    <para>By using $activate == 0 it is possible to
                    create multiple namespace declarations on a single
                    element.</para>
                    <para>The function fails if it is required to
                      create a declaration associating the prefix
                      with the namespace URI but the element already
                      carries a declaration with the same prefix but
                      different namespace URI.
                    </para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>setNamespaceDeclURI</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;setNamespaceDeclURI( $nsPrefix, $newURI );</funcsynopsisinfo>
                    </funcsynopsis>
	            <para>EXPERIMENTAL IN 1.61 !</para>
                    <para>This function manipulates
	            directly with an existing namespace
                    declaration on an element. It takes
                    two parameters: the prefix by which it
	            looks up the namespace declaration and
                    a new namespace URI which replaces its previous
	            value.</para>
	            <para>It returns 1 if the namespace declaration
	            was found and changed, 0 otherwise.</para>
	            <para>All elements and attributes (even those previously
	             unbound from the document) for which the
                     namespace declaration determines their namespace
                     belong to the new namespace after
	             the change.
           	  </para>
	          <para>If the new URI is undef or empty, the nodes
	             have no namespace and no prefix after the change.
	             Namespace declarations
	             once nulled in this way do not
	             further appear in the serialized output
	             (but do remain in the document for internal integrity
	             of libxml2 data structures).
               	  </para>
             	  <para>This function is NOT part of any DOM API.</para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>setNamespaceDeclPrefix</term>
                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node-&gt;setNamespaceDeclPrefix( $oldPrefix, $newPrefix );</funcsynopsisinfo>
                    </funcsynopsis>
	            <para>EXPERIMENTAL IN 1.61 !</para>
                    <para>This function manipulates
	            directly with an existing namespace
                    declaration on an element. It takes
                    two parameters: the old prefix by which it
	            looks up the namespace declaration and
                    a new prefix which is to replace the old one.</para>
	            <para>The function dies with an error
	             if the element is in the scope of
	             another declaration whose prefix equals
	             to the new prefix, or if the change should
                     result in a declaration with a non-empty prefix but
	             empty namespace URI.
	             Otherwise, it returns 1 if the namespace declaration
	             was found and changed and 0 if not found.</para>
	            <para>All elements and attributes (even those previously
	             unbound from the document) for which the
                     namespace declaration determines their namespace
	             change their prefix to the new value.
           	  </para>
	          <para>If the new prefix is undef or empty,
	             the namespace declaration becomes
                     a declaration of a default namespace.
                     The corresponding nodes drop their namespace prefix
	             (but remain in the, now default, namespace).
	             In this case the function fails, if the containing element
	             is in the scope of another default namespace declaration.
               	  </para>
             	  <para>This function is NOT part of any DOM API.</para>
                </listitem>
            </varlistentry>

        </variablelist>
	</sect1>
	<sect1>
	  <title>Overloading</title>
	  <para>XML::LibXML::Element overloads hash dereferencing to
	  provide access to the element's attributes. For non-namespaced
	  attributes, the attribute name is the hash key, and the attribute
	  value is the hash value. For namespaced attributes, the hash key
	  is qualified with the namespace URI, using Clark notation.</para>
          <para>Perl's "tied hash" feature is used, which means that the
	  hash gives you read-write access to the element's attributes.
          For more information, see <olink targetdoc="XML::LibXML::AttributeHash"
          >XML::LibXML::AttributeHash</olink></para>
	</sect1>
    </chapter>

    <chapter id="XML-LibXML-Text">
        <title>XML::LibXML Class for Text Nodes</title>

        <titleabbrev>XML::LibXML::Text</titleabbrev>
        <sect1>
            <title>Synopsis</title>
            <programlisting>use XML::LibXML;
# Only methods specific to Text nodes are listed here,
# see the XML::LibXML::Node manpage for other methods</programlisting>
        </sect1>
        <sect1>
            <title>Description</title>

        <para>Unlike the DOM specification, XML::LibXML implements the text node as the base class of all character data node. Therefore there exists no
        CharacterData class. This allows one to apply methods of text nodes also to Comments and CDATA-sections.</para>
	</sect1>
        <sect1>
            <title>Methods</title>
	  <para>
	    The class inherits from <xref linkend="XML-LibXML-Node"/>.
	    The documentation for Inherited methods is not listed here.
	  </para>
	  <para>
	    Many functions listed here are
	    extensively documented in the <ulink url="http://www.w3.org/TR/DOM-Level-3-Core/">DOM Level 3 specification</ulink>. Please refer to
	    the specification for extensive documentation.
	  </para>

        <variablelist>
            <varlistentry>
                <term>new</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$text = XML::LibXML::Text-&gt;new( $content ); </funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The constructor of the class. It creates an unbound text node.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>data</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$nodedata = $text-&gt;data;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Although there exists the <function>nodeValue</function> attribute in the Node class, the DOM specification defines data as a separate
                    attribute. <function>XML::LibXML</function> implements these two attributes not as different attributes, but as aliases, such as
                    <function>libxml2</function> does. Therefore</para>

                    <programlisting> $text-&gt;data;</programlisting>

                    <para>and</para>

                    <programlisting> $text-&gt;nodeValue;</programlisting>

                    <para>will have the same result and are not different entities.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>setData($string)</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$text-&gt;setData( $text_content );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function sets or replaces text content to a node. The node has to be of the type "text", "cdata" or
                    "comment".</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>substringData($offset,$length)</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$text-&gt;substringData($offset, $length);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Extracts a range of data from the node. (DOM Spec) This function takes the two parameters $offset and $length and returns the
                    sub-string, if available.</para>

                    <para>If the node contains no data or $offset refers to an non-existing string index, this function will return <emphasis>undef</emphasis>.
                    If $length is out of range <function>substringData</function> will return the data starting at $offset instead of causing an error.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>appendData($string)</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$text-&gt;appendData( $somedata );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Appends a string to the end of the existing data. If the current text node contains no data, this function has the same effect as
                    <function>setData</function>.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>insertData($offset,$string)</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$text-&gt;insertData($offset, $string);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Inserts the parameter $string at the given $offset of the existing data of the node. This operation will not remove existing data, but
                    change the order of the existing data.</para>

                    <para>The $offset has to be a positive value. If $offset is out of range, <function>insertData</function> will have the same behaviour as
                    <function>appendData</function>.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>deleteData($offset, $length)</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$text-&gt;deleteData($offset, $length);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This method removes a chunk from the existing node data at the given offset. The $length parameter tells, how many characters should
                    be removed from the string.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>deleteDataString($string, [$all])</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$text-&gt;deleteDataString($remstring, $all);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This method removes a chunk from the existing node data. Since the DOM spec is quite unhandy if you already know <function>which</function>
                    string to remove from a text node, this method allows more perlish code :)</para>

                    <para>The functions takes two parameters: <emphasis>$string</emphasis> and optional the <emphasis>$all</emphasis> flag. If $all is not set,
                    <emphasis>undef</emphasis> or <emphasis>0</emphasis>, <function>deleteDataString</function> will remove only the first occurrence of
                    $string. If $all is <emphasis>TRUE</emphasis> <function>deleteDataString</function> will remove all occurrences of <emphasis>$string</emphasis>
                    from the node data.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>replaceData($offset, $length, $string)</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$text-&gt;replaceData($offset, $length, $string);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The DOM style version to replace node data.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>replaceDataString($oldstring, $newstring, [$all])</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$text-&gt;replaceDataString($old, $new, $flag);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The more programmer friendly version of replaceData() :)</para>

                    <para>Instead of giving offsets and length one can specify
                        the exact string (<emphasis>$oldstring</emphasis>) to
                        be replaced. Additionally the <emphasis>$all</emphasis>
                        flag allows one to replace all occurrences of
                        <emphasis>$oldstring</emphasis>.</para>

                </listitem>
            </varlistentry>



            <varlistentry>
                <term>replaceDataRegEx( $search_cond, $replace_cond, $reflags )</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$text-&gt;replaceDataRegEx( $search_cond, $replace_cond, $reflags );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This method replaces the node's data by a
                        <function>simple</function> regular expression.
                        Optional, this function allows one to pass some flags
                        that will be added as flag to the replace
                        statement.</para>

                    <para><emphasis>NOTE:</emphasis> This is a shortcut for</para>

                    <programlisting> my $datastr = $node-&gt;getData();
 $datastr =~ s/somecond/replacement/g; # 'g' is just an example for any flag
 $node-&gt;setData( $datastr );</programlisting>

                    <para>This function can make things easier to read for simple replacements. For more complex variants it is recommended to use the code
                    snippet above.</para>
                </listitem>
            </varlistentry>
        </variablelist>
	</sect1>
    </chapter>

    <chapter id="XML-LibXML-Comment">
        <title>XML::LibXML Comment Class</title>

        <titleabbrev>XML::LibXML::Comment</titleabbrev>
        <sect1>
            <title>Synopsis</title>
            <programlisting>use XML::LibXML;
# Only methods specific to Comment nodes are listed here,
# see the XML::LibXML::Node manpage for other methods</programlisting>
        </sect1>
        <sect1>
            <title>Description</title>

        <para>This class provides all functions of <xref linkend="XML-LibXML-Text"/>, but for comment nodes. This can be done, since only the output of the
        node types is different, but not the data structure. :-)</para>
	</sect1>
        <sect1>
            <title>Methods</title>
	  <para>
	    The class inherits from <xref linkend="XML-LibXML-Node"/>.
	    The documentation for Inherited methods is not listed here.
	  </para>
	  <para>
	    Many functions listed here are
	    extensively documented in the <ulink url="http://www.w3.org/TR/DOM-Level-3-Core/">DOM Level 3 specification</ulink>. Please refer to
	    the specification for extensive documentation.
	  </para>

        <variablelist>
            <varlistentry>
                <term>new</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node = XML::LibXML::Comment-&gt;new( $content );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The constructor is the only provided function for this package. It is required, because <emphasis>libxml2</emphasis> treats text nodes
                    and comment nodes slightly differently.</para>
                </listitem>
            </varlistentry>
        </variablelist>
	</sect1>
    </chapter>

    <chapter id="XML-LibXML-CDATASection">
        <title>XML::LibXML Class for CDATA Sections</title>

        <titleabbrev>XML::LibXML::CDATASection</titleabbrev>
        <sect1>
            <title>Synopsis</title>
            <programlisting>use XML::LibXML;
# Only methods specific to CDATA nodes are listed here,
# see the XML::LibXML::Node manpage for other methods</programlisting>
        </sect1>
	<sect1>
	  <title>Description</title>
        <para>This class provides all functions of <xref linkend="XML-LibXML-Text"/>, but for CDATA nodes.</para>
	</sect1>
        <sect1>
            <title>Methods</title>
	  <para>
	    The class inherits from <xref linkend="XML-LibXML-Node"/>.
	    The documentation for Inherited methods is not listed here.
	  </para>
	  <para>
	    Many functions listed here are
	    extensively documented in the <ulink url="http://www.w3.org/TR/DOM-Level-3-Core/">DOM Level 3 specification</ulink>. Please refer to
	    the specification for extensive documentation.
	  </para>


        <variablelist>
            <varlistentry>
                <term>new</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node = XML::LibXML::CDATASection-&gt;new( $content );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The constructor is the only provided function for this package. It is required, because <emphasis>libxml2</emphasis> treats the
                    different text node types slightly differently.</para>
                </listitem>
            </varlistentry>
        </variablelist>
	</sect1>
    </chapter>

    <chapter id="XML-LibXML-Attr">
        <title>XML::LibXML Attribute Class</title>

        <titleabbrev>XML::LibXML::Attr</titleabbrev>
        <sect1>
            <title>Synopsis</title>
            <programlisting>use XML::LibXML;
# Only methods specific to Attribute nodes are listed here,
# see the XML::LibXML::Node manpage for other methods</programlisting>
        </sect1>
	<sect1>
	  <title>Description</title>

        <para>This is the interface to handle Attributes like ordinary nodes. The naming of the class relies on the W3C DOM documentation.</para>
	</sect1>
        <sect1>
            <title>Methods</title>
	  <para>
	    The class inherits from <xref linkend="XML-LibXML-Node"/>.
	    The documentation for Inherited methods is not listed here.
	  </para>
	  <para>
	    Many functions listed here are
	    extensively documented in the <ulink url="http://www.w3.org/TR/DOM-Level-3-Core/">DOM Level 3 specification</ulink>. Please refer to
	    the specification for extensive documentation.
	  </para>
        <variablelist>
            <varlistentry>
                <term>new</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$attr = XML::LibXML::Attr-&gt;new($name [,$value]);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Class constructor. If you need to work with ISO encoded strings, you should <emphasis>always</emphasis> use the <function>createAttribute</function>
                    of <xref linkend="XML-LibXML-Document"/>.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>getValue</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$string = $attr-&gt;getValue();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the value stored for the attribute. If undef is returned, the attribute has no value, which is different of being
                    <function>not specified</function>.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>value</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$string = $attr-&gt;value;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Alias for <emphasis>getValue()</emphasis></para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>setValue</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$attr-&gt;setValue( $string );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This is needed to set a new attribute value. If ISO encoded strings are passed as parameter, the node has to be bound to a document,
                    otherwise the encoding might be done incorrectly.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>getOwnerElement</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$node = $attr-&gt;getOwnerElement();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>returns the node the attribute belongs to. If the attribute is not bound to a node, undef will be returned. Overwriting the underlying
                    implementation, the <emphasis>parentNode</emphasis> function will return undef, instead of the owner element.</para>
                </listitem>
            </varlistentry>



            <varlistentry>
                <term>setNamespace</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$attr-&gt;setNamespace($nsURI, $prefix);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function tries to bound the attribute to a given namespace.
            If <function>$nsURI</function> is undefined or empty,
            the function discards any previous association of the attribute with a namespace.
	    If the namespace was not previously declared in the context of the
	    attribute, this function will fail.
	    In this case you may wish to call setNamespace() on the ownerElement.
	    If the namespace URI is non-empty and
	    declared in the context of the attribute, but only with a different
	    (non-empty) prefix, then the attribute is still bound to the namespace
	    but gets a different prefix than <function>$prefix</function>.
	    The function also fails if the prefix is empty but the namespace URI
	    is not (because unprefixed attributes should by definition belong to
	    no namespace).
	    This function returns 1 on success, 0 otherwise.
	  </para>
                </listitem>
            </varlistentry>


            <varlistentry>
                <term>isId</term>
                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$bool = $attr-&gt;isId;</funcsynopsisinfo>
                    </funcsynopsis>
                    <para>Determine whether an attribute is of type
		      ID. For documents with a DTD, this information
                      is only available if DTD loading/validation has been requested.
                      For HTML documents parsed with the HTML
		      parser ID detection is done
		      automatically. In XML documents, all "xml:id"
		      attributes are considered to be of type ID.
		    </para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>serializeContent($docencoding)</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$string = $attr-&gt;serializeContent;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function is not part of DOM API. It returns attribute content
                       in the form in which it serializes into XML, that is
	               with all meta-characters properly quoted and with raw
	               entity references (except for entities expanded during parse time).
	               Setting the optional $docencoding flag to 1 enforces document
	               encoding for the output string (which is then passed to Perl as a
	               byte string). Otherwise the string is passed to Perl as (UTF-8 encoded)
	               characters.
                    </para>
                </listitem>
            </varlistentry>

        </variablelist>
	</sect1>
    </chapter>

    <chapter id="XML-LibXML-DocumentFragment">
        <title>XML::LibXML's DOM L2 Document Fragment Implementation</title>

        <titleabbrev>XML::LibXML::DocumentFragment</titleabbrev>
        <sect1>
            <title>Synopsis</title>
            <programlisting>use XML::LibXML;</programlisting>
        </sect1>
        <sect1>
            <title>Description</title>

        <para>This class is a helper class as described in the DOM Level 2 Specification. It is implemented as a node without name. All adding, inserting or
        replacing functions are aware of document fragments now.</para>

        <para>As well <emphasis>all</emphasis> unbound nodes (all nodes that do not belong to any document sub-tree) are implicit members of document fragments.</para>
	</sect1>
    </chapter>

    <chapter id="XML-LibXML-Namespace">
        <title>XML::LibXML Namespace Implementation</title>

        <titleabbrev>XML::LibXML::Namespace</titleabbrev>
        <sect1>
            <title>Synopsis</title>
            <programlisting>use XML::LibXML;
# Only methods specific to Namespace nodes are listed here,
# see the XML::LibXML::Node manpage for other methods</programlisting>
        </sect1>
	<sect1>
	  <title>Description</title>

        <para>Namespace nodes are returned by both $element-&gt;findnodes('namespace::foo') or by $node-&gt;getNamespaces().</para>

        <para>The namespace node API is not part of any current DOM API, and so it is quite minimal. It should be noted that namespace nodes are
        <emphasis>not</emphasis> a sub class of <xref linkend="XML-LibXML-Node"/>, however Namespace nodes act a lot like attribute nodes, and similarly named methods will
        return what you would expect if you treated the namespace node as an attribute. Note that in order to fix several inconsistencies between the API and the documentation, the behavior of some functions have been changed in 1.64.</para>
	</sect1>
        <sect1>
            <title>Methods</title>
        <variablelist>
            <varlistentry>
                <term>new</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>my $ns = XML::LibXML::Namespace-&gt;new($nsURI);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Creates a new Namespace node. Note that this is not a 'node' as an attribute or an element node. Therefore you can't do
                    call all <xref linkend="XML-LibXML-Node"/> Functions. All functions available for this node are listed below.</para>

                    <para>Optionally you can pass the prefix to the namespace constructor. If this second parameter is omitted you will create a so called
                    default namespace. Note, the newly created namespace is not bound to any document or node, therefore you should not expect it to be
                    available in an existing document.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>declaredURI</term>
                <listitem>
                   <para>Returns the URI for this namespace.</para>
		</listitem>
            </varlistentry>
            <varlistentry>
                <term>declaredPrefix</term>
                <listitem>
                   <para>Returns the prefix for this namespace.</para>
		</listitem>
            </varlistentry>

            <varlistentry>
                <term>nodeName</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>print $ns-&gt;nodeName();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns "xmlns:prefix", where prefix is the prefix for this namespace.</para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>name</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>print $ns-&gt;name();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Alias for nodeName()</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>getLocalName</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$localname = $ns-&gt;getLocalName();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the local name of this node as if it were an attribute, that is, the prefix associated with the namespace.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>getData</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>print $ns-&gt;getData();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the URI of the namespace, i.e. the value of this node as if it were an attribute.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>getValue</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>print $ns-&gt;getValue();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Alias for getData()</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>value</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>print $ns-&gt;value();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Alias for getData()</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>getNamespaceURI</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$known_uri = $ns-&gt;getNamespaceURI();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the string "http://www.w3.org/2000/xmlns/"</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>getPrefix</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$known_prefix = $ns-&gt;getPrefix();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the string "xmlns"</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>unique_key</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$key = $ns-&gt;unique_key();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This method returns a key guaranteed to be unique for this namespace, and to always be the same value for this namespace. Two namespace objects return the same key if and only if they have the same prefix and the same URI. The returned key value is useful as a key in hashes.</para>
                </listitem>
            </varlistentry>
        </variablelist>
	</sect1>
    </chapter>

    <chapter id="XML-LibXML-PI">
        <title>XML::LibXML Processing Instructions</title>

        <titleabbrev>XML::LibXML::PI</titleabbrev>
        <sect1>
            <title>Synopsis</title>
            <programlisting>use XML::LibXML;
# Only methods specific to Processing Instruction nodes are listed here,
# see the XML::LibXML::Node manpage for other methods</programlisting>
        </sect1>
	<sect1>
	  <title>Description</title>

        <para>Processing instructions are implemented with XML::LibXML with read and write access. The PI data is the PI without the PI target (as specified in
        XML 1.0 [17]) as a string. This string can be accessed with getData as implemented in <xref linkend="XML-LibXML-Node"/>.</para>

        <para>The write access is aware about the fact, that many processing instructions have attribute like data. Therefore setData() provides besides the DOM
        spec conform Interface to pass a set of named parameter. So the code segment</para>

        <programlisting>my $pi = $dom-&gt;createProcessingInstruction("abc");
$pi-&gt;setData(foo=&gt;'bar', foobar=&gt;'foobar');
$dom-&gt;appendChild( $pi );</programlisting>

        <para>will result the following PI in the DOM:</para>

        <programlisting>&lt;?abc foo="bar" foobar="foobar"?&gt;</programlisting>

        <para>Which is how it is specified in the DOM specification. This three step interface creates temporary a node in perl space. This can be avoided while
        using the insertProcessingInstruction() method. Instead of the three calls described above, the call</para>

        <programlisting>$dom-&gt;insertProcessingInstruction("abc",'foo="bar" foobar="foobar"');</programlisting>

        <para>will have the same result as above.</para>

        <para><xref linkend="XML-LibXML-PI"/>'s implementation of setData() documented below differs a bit from the standard version as available in <xref linkend="XML-LibXML-Node"/>:</para>
        <variablelist>
            <varlistentry>
                <term>setData</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$pinode-&gt;setData( $data_string );
$pinode-&gt;setData( name=&gt;string_value [...] );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This method allows one to change the content data of
                        a PI. Additionally to the interface specified for DOM
                        Level2, the method provides a named parameter
                        interface to set the data. This parameter list is
                        converted into a string before it is appended to the
                        PI.</para>
                </listitem>
            </varlistentry>
        </variablelist>
	</sect1>
    </chapter>

    <chapter id="XML-LibXML-Dtd">
        <title>XML::LibXML DTD Handling</title>

        <titleabbrev>XML::LibXML::Dtd</titleabbrev>
        <sect1>
            <title>Synopsis</title>
            <programlisting>use XML::LibXML;</programlisting>
        </sect1>
        <sect1>
            <title>Description</title>

        <para>This class holds a DTD. You may parse a DTD from either a string, or from an external SYSTEM identifier.</para>

        <para>No support is available as yet for parsing from a filehandle.</para>

        <para>XML::LibXML::Dtd is a sub-class of <xref linkend="XML-LibXML-Node"/>, so all the methods available to nodes (particularly toString()) are available to Dtd objects.</para>
	</sect1>
        <sect1>
            <title>Methods</title>


        <variablelist>
            <varlistentry>
                <term>new</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$dtd = XML::LibXML::Dtd-&gt;new($public_id, $system_id);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Parse a DTD from the system identifier, and return a DTD object that you can pass to $doc-&gt;is_valid() or $doc-&gt;validate().</para>

                    <programlisting> my $dtd = XML::LibXML::Dtd-&gt;new(
                      "SOME // Public / ID / 1.0",
                      "test.dtd"
                                );
 my $doc = XML::LibXML-&gt;new-&gt;parse_file("test.xml");
 $doc-&gt;validate($dtd);</programlisting>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>parse_string</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$dtd = XML::LibXML::Dtd-&gt;parse_string($dtd_str);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The same as new() above, except you can parse a DTD from a string. Note that parsing from string may fail if the DTD contains external parametric-entity references with relative URLs.</para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>getName</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$publicId = $dtd-&gt;getName();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the name of DTD; i.e., the name immediately following the DOCTYPE keyword.</para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>publicId</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$publicId = $dtd-&gt;publicId();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the public identifier of the external subset.</para>
                </listitem>
            </varlistentry>
            <varlistentry>
                <term>systemId</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$systemId = $dtd-&gt;systemId();</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the system identifier of the external subset.</para>
                </listitem>
            </varlistentry>
        </variablelist>
	</sect1>
    </chapter>

    <chapter id="XML-LibXML-InputCallback">
        <title>XML::LibXML Class for Input Callbacks</title>

        <titleabbrev>XML::LibXML::InputCallback</titleabbrev>
        <sect1>
            <title>Synopsis</title>
            <programlisting>use XML::LibXML;</programlisting>
        </sect1>

        <sect1>
            <title>Synopsis</title>

            <programlisting>my $input_callbacks = XML::LibXML::InputCallback-&gt;new();
$input_callbacks-&gt;register_callbacks([ $match_cb1, $open_cb1,
                                       $read_cb1, $close_cb1 ] );
$input_callbacks-&gt;register_callbacks([ $match_cb2, $open_cb2,
                                       $read_cb2, $close_cb2 ] );
$input_callbacks-&gt;register_callbacks( [ $match_cb3, $open_cb3,
                                        $read_cb3, $close_cb3 ] );

$parser-&gt;input_callbacks( $input_callbacks );
$parser-&gt;parse_file( $some_xml_file );</programlisting>
        </sect1>

        <sect1>
            <title>Description</title>

            <para>You may get unexpected results if you are trying to load external documents during libxml2 parsing if the location of the resource is not a
            HTTP, FTP or relative location but a absolute path for example. To get around this limitation, you may add your own input handler to open, read and
            close particular types of locations or URI classes. Using this input callback handlers, you can handle your own custom URI schemes for example.</para>

            <para>The input callbacks are used whenever XML::LibXML has to get something other than externally parsed entities from somewhere. They are implemented
            using a callback stack on the Perl layer in analogy to libxml2's native callback stack.</para>

            <para>The XML::LibXML::InputCallback class transparently registers the input callbacks for the libxml2's parser processes.</para>

            <sect2>
                <title>How does XML::LibXML::InputCallback work?</title>

                <para>The libxml2 library offers a callback implementation as global functions only. To work-around the troubles resulting in having only global
                callbacks - for example, if the same global callback stack is manipulated by different applications running together in a single Apache
                Web-server environment -, XML::LibXML::InputCallback comes with a object-oriented and a function-oriented part.</para>

                <para>Using the function-oriented part the global callback stack of libxml2 can be manipulated. Those functions can be used as interface to the
                callbacks on the C- and XS Layer. At the object-oriented part, operations for working with the "pseudo-localized" callback stack are
                implemented. Currently, you can register and de-register callbacks on the Perl layer and initialize them on a per parser basis.</para>

                <sect3>
                    <title>Callback Groups</title>

                    <para>The libxml2 input callbacks come in groups. One group contains a URI matcher (<emphasis>match</emphasis>), a data stream constructor (<emphasis>open</emphasis>),
                    a data stream reader (<emphasis>read</emphasis>), and a data stream destructor (<emphasis>close</emphasis>). The callbacks can be
                    manipulated on a per group basis only.</para>
                </sect3>

                <sect3>
                    <title>The Parser Process</title>

                    <para>The parser process works on an XML data stream, along which, links to other resources can be embedded. This can be links to external
                    DTDs or XIncludes for example. Those resources are identified by URIs. The callback implementation of libxml2 assumes that one callback
                    group can handle a certain amount of URIs and a certain URI scheme. Per default, callback handlers for <emphasis>file://*</emphasis>,
                    <emphasis>file:://*.gz</emphasis>, <emphasis>http://*</emphasis> and <emphasis>ftp://*</emphasis> are registered.</para>

                    <para>Callback groups in the callback stack are processed from top to bottom, meaning that callback groups registered later will be
                    processed before the earlier registered ones.</para>

                    <para>While parsing the data stream, the libxml2 parser checks if a registered callback group will handle a URI - if they will not, the URI
                    will be interpreted as <emphasis>file://URI</emphasis>. To handle a URI, the <emphasis>match</emphasis> callback will have to return
                    '1'. If that happens, the handling of the URI will be passed to that callback group. Next, the URI will be passed to the
                    <emphasis>open</emphasis> callback, which should return a <emphasis>reference</emphasis> to the data stream if it successfully opened the
                    file, '0' otherwise. If opening the stream was successful, the <emphasis>read</emphasis> callback will be called repeatedly until it
                    returns an empty string. After the read callback, the <emphasis>close</emphasis> callback will be called to close the stream.</para>
                </sect3>

                <sect3>
                    <title>Organisation of callback groups in XML::LibXML::InputCallback</title>

                    <para>Callback groups are implemented as a stack (Array),
                        each entry holds a reference to an array of the
                        callbacks. For the libxml2 library, the
                        XML::LibXML::InputCallback callback implementation
                        appears as one single callback group. The Perl
                        implementation however allows one to manage different
                        callback stacks on a per libxml2-parser basis.</para>
                </sect3>
            </sect2>

            <sect2>
                <title>Using XML::LibXML::InputCallback</title>

                <para>After object instantiation using the parameter-less constructor, you can register callback groups.</para>

                <programlisting>my $input_callbacks = XML::LibXML::InputCallback-&gt;new();
$input_callbacks-&gt;register_callbacks([ $match_cb1, $open_cb1,
                                       $read_cb1, $close_cb1 ] );
$input_callbacks-&gt;register_callbacks([ $match_cb2, $open_cb2,
                                       $read_cb2, $close_cb2 ] );
$input_callbacks-&gt;register_callbacks( [ $match_cb3, $open_cb3,
                                        $read_cb3, $close_cb3 ] );

$parser-&gt;input_callbacks( $input_callbacks );
$parser-&gt;parse_file( $some_xml_file );</programlisting>
            </sect2>

            <sect2>
                <title>What about the old callback system prior to XML::LibXML::InputCallback?</title>

                <para>In XML::LibXML versions prior to 1.59 - i.e. without the XML::LibXML::InputCallback module - you could define your callbacks either using
                globally or locally. You still can do that using XML::LibXML::InputCallback, and in addition to that you can define the callbacks on a per
                parser basis!</para>

                <para>If you use the old callback interface through global callbacks, XML::LibXML::InputCallback will treat them with a lower priority as the
                ones registered using the new interface. The global callbacks will not override the callback groups registered using the new interface. Local
                callbacks are attached to a specific parser instance, therefore they are treated with highest priority. If the <emphasis>match</emphasis>
                callback of the callback group registered as local variable is identical to one of the callback groups registered using the new interface, that
                callback group will be replaced.</para>

                <para>Users of the old callback implementation whose <emphasis>open</emphasis> callback returned a plain string, will have to adapt their code
                to return a reference to that string after upgrading to version &gt;= 1.59. The new callback system can only deal with the
                <emphasis>open</emphasis> callback returning a reference!</para>
            </sect2>
        </sect1>

        <sect1>
            <title>Interface Description</title>

            <sect2>
                <title>Global Variables</title>

                <variablelist>
                    <varlistentry>
                        <term>$_CUR_CB</term>

                        <listitem>
                            <para>Stores the current callback and can be used as shortcut to access the callback stack.</para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>@_GLOBAL_CALLBACKS</term>

                        <listitem>
                            <para>Stores all callback groups for the current parser process.</para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>@_CB_STACK</term>

                        <listitem>
                            <para>Stores the currently used callback group. Used to prevent parser errors when dealing with nested XML data.</para>
                        </listitem>
                    </varlistentry>
                </variablelist>
            </sect2>

            <sect2>
                <title>Global Callbacks</title>

                <variablelist>
                    <varlistentry>
                        <term>_callback_match</term>

                        <listitem>
                            <para>Implements the interface for the <emphasis>match</emphasis> callback at C-level and for the selection of the callback group
                            from the callbacks defined at the Perl-level.</para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>_callback_open</term>

                        <listitem>
                            <para>Forwards the <emphasis>open</emphasis> callback from libxml2 to the corresponding callback function at the Perl-level.</para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>_callback_read</term>

                        <listitem>
                            <para>Forwards the read request to the corresponding callback function at the Perl-level and returns the result to libxml2.</para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>_callback_close</term>

                        <listitem>
                            <para>Forwards the <emphasis>close</emphasis> callback from libxml2 to the corresponding callback function at the Perl-level..</para>
                        </listitem>
                    </varlistentry>
                </variablelist>
            </sect2>

            <sect2>
                <title>Class methods</title>

                <variablelist>
                    <varlistentry>
                        <term>new()</term>

                        <listitem>
                            <para>A simple constructor.</para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>register_callbacks( [ $match_cb, $open_cb, $read_cb, $close_cb ])</term>

                        <listitem>
                            <para>The four callbacks <emphasis>have</emphasis> to be given as array reference in the above order <emphasis>match</emphasis>,
                            <emphasis>open</emphasis>, <emphasis>read</emphasis>, <emphasis>close</emphasis>!</para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>unregister_callbacks( [ $match_cb, $open_cb, $read_cb, $close_cb ])</term>

                        <listitem>
                            <para>With no arguments given, <function>unregister_callbacks()</function> will delete the last registered callback group from the
                            stack. If four callbacks are passed as array reference, the callback group to unregister will be identified by the
                            <emphasis>match</emphasis> callback and deleted from the callback stack. Note that if several identical <emphasis>match</emphasis>
                            callbacks are defined in different callback groups, ALL of them will be deleted from the stack.</para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>init_callbacks( $parser )</term>

                        <listitem>
                            <para>Initializes the callback system for the provided parser before starting a parsing process.</para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>cleanup_callbacks()</term>

                        <listitem>
                            <para>Resets global variables and the libxml2 callback stack.</para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>lib_init_callbacks()</term>

                        <listitem>
                            <para>Used internally for callback registration at C-level.</para>
                        </listitem>
                    </varlistentry>

                    <varlistentry>
                        <term>lib_cleanup_callbacks()</term>

                        <listitem>
                            <para>Used internally for callback resetting at the C-level.</para>
                        </listitem>
                    </varlistentry>
                </variablelist>

                <para/>
            </sect2>
        </sect1>

        <sect1>
            <title>Example callbacks</title>

            <para>The following example is a purely fictitious example that uses a MyScheme::Handler object that responds to methods similar to an IO::Handle.</para>

            <programlisting>
# Define the four callback functions
sub match_uri {
    my $uri = shift;
    return $uri =~ /^myscheme:/; # trigger our callback group at a 'myscheme' URIs
}

sub open_uri {
    my $uri = shift;
    my $handler = MyScheme::Handler-&gt;new($uri);
    return $handler;
}

# The returned $buffer will be parsed by the libxml2 parser
sub read_uri {
    my $handler = shift;
    my $length = shift;
    my $buffer;
    read($handler, $buffer, $length);
    return $buffer; # $buffer will be an empty string '' if read() is done
}

# Close the handle associated with the resource.
sub close_uri {
    my $handler = shift;
    close($handler);
}

# Register them with a instance of XML::LibXML::InputCallback
my $input_callbacks = XML::LibXML::InputCallback-&gt;new();
$input_callbacks-&gt;register_callbacks([ \&amp;match_uri, \&amp;open_uri,
                                       \&amp;read_uri, \&amp;close_uri ] );

# Register the callback group at a parser instance
$parser-&gt;input_callbacks( $input_callbacks );

# $some_xml_file will be parsed using our callbacks
$parser-&gt;parse_file( $some_xml_file );


</programlisting>
        </sect1>
    </chapter>

    <chapter id="XML-LibXML-RelaxNG">
        <title>RelaxNG Schema Validation</title>

        <titleabbrev>XML::LibXML::RelaxNG</titleabbrev>
        <sect1>
            <title>Synopsis</title>
            <programlisting>use XML::LibXML;
$doc = XML::LibXML-&gt;new-&gt;parse_file($url);</programlisting>
        </sect1>
        <sect1>
            <title>Description</title>

        <para>The XML::LibXML::RelaxNG class is a tiny frontend to libxml2's RelaxNG implementation. Currently it supports only schema parsing and document
        validation.</para>
	</sect1>
        <sect1>
            <title>Methods</title>

        <variablelist>
            <varlistentry>
                <term>new</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$rngschema = XML::LibXML::RelaxNG-&gt;new( location =&gt; $filename_or_url );
$rngschema = XML::LibXML::RelaxNG-&gt;new( string =&gt; $xmlschemastring );
$rngschema = XML::LibXML::RelaxNG-&gt;new( DOM =&gt; $doc );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The constructor of XML::LibXML::RelaxNG may get called with either one of three parameters. The parameter tells the class from which
                    source it should generate a validation schema. It is important, that each schema only have a single source.</para>

                <para>The location parameter allows one to parse a schema
                    from the filesystem or a URL.</para>

                    <para>The string parameter will parse the schema from the given XML string.</para>

                    <para>The DOM parameter allows one to parse the schema from a pre-parsed <xref linkend="XML-LibXML-Document"/>.</para>

                    <para>Note that the constructor will die() if the schema does not meed the constraints of the RelaxNG specification.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>validate</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>eval { $rngschema-&gt;validate( $doc ); };</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function allows one to validate a (parsed)
                        document against the given RelaxNG schema. The argument
                        of this function should be an XML::LibXML::Document
                        object.  If this function succeeds, it will return 0,
                        otherwise it will die() and report the errors found.
                        Because of this validate() should be always
                        evaluated.</para>

                </listitem>
            </varlistentry>
        </variablelist>
	</sect1>
    </chapter>

    <chapter id="XML-LibXML-Schema">
        <title>XML Schema Validation</title>

        <titleabbrev>XML::LibXML::Schema</titleabbrev>
        <sect1>
            <title>Synopsis</title>
            <programlisting>use XML::LibXML;
$doc = XML::LibXML-&gt;new-&gt;parse_file($url);</programlisting>
        </sect1>
        <sect1>
            <title>Description</title>

        <para>The XML::LibXML::Schema class is a tiny frontend to libxml2's XML Schema implementation. Currently it supports only schema parsing and
        document validation. As of 2.6.32, libxml2 only supports decimal types up to 24 digits (the standard requires at least 18).
	</para>
	</sect1>
        <sect1>
            <title>Methods</title>
        <variablelist>
            <varlistentry>
                <term>new</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$xmlschema = XML::LibXML::Schema-&gt;new( location =&gt; $filename_or_url );
$xmlschema = XML::LibXML::Schema-&gt;new( string =&gt; $xmlschemastring );</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>The constructor of XML::LibXML::Schema may get called with either one of two parameters. The parameter tells the class from which
                    source it should generate a validation schema. It is important, that each schema only have a single source.</para>

                <para>The location parameter allows one to parse a schema
                    from the filesystem or a URL.</para>

                    <para>The string parameter will parse the schema from the given XML string.</para>

                    <para>Note that the constructor will die() if the schema does not meed the constraints of the XML Schema specification.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>validate</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>eval { $xmlschema-&gt;validate( $doc ); };</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>This function allows one to validate a (parsed)
                        document against the given XML Schema.  The argument of
                        this function should be a <xref
                            linkend="XML-LibXML-Document"/> object.  If this
                        function succeeds, it will return 0, otherwise it will
                        die() and report the errors found. Because of this
                        validate() should be always evaluated.</para>

                </listitem>
            </varlistentry>
        </variablelist>
	</sect1>
    </chapter>
  <chapter id="XML-LibXML-XPathContext">
    <title>XPath Evaluation</title>
    <titleabbrev>XML::LibXML::XPathContext</titleabbrev>
    <sect1>
      <title>Description</title>
      <para>
        The XML::LibXML::XPathContext
        class provides an almost complete
        interface to libxml2's XPath implementation.
        With XML::LibXML::XPathContext, it is possible to
        evaluate XPath expressions in the context
        of arbitrary node, context size, and context position,
        with a user-defined namespace-prefix mapping,
        custom XPath functions written in Perl, and
        even a custom XPath variable resolver.
    </para>
    </sect1>
    <sect1>
      <title>Examples</title>
      <sect2>
        <title>Namespaces</title>
<para>This example demonstrates <function>registerNs()</function> method.
It finds all paragraph nodes in an XHTML document.</para>
          <programlisting>my $xc = XML::LibXML::XPathContext-&gt;new($xhtml_doc);
$xc-&gt;registerNs('xhtml', 'http://www.w3.org/1999/xhtml');
my @nodes = $xc-&gt;findnodes('//xhtml:p');</programlisting>
      </sect2>
      <sect2>
        <title>Custom XPath functions</title>
<para>This example demonstrates <function>registerFunction()</function> method
by defining a function filtering nodes based on a Perl regular expression:</para>
	<programlisting>sub grep_nodes {
  my ($nodelist,$regexp) =  @_;
  my $result = XML::LibXML::NodeList-&gt;new;
  for my $node ($nodelist-&gt;get_nodelist()) {
    $result-&gt;push($node) if $node-&gt;textContent =~ $regexp;
  }
  return $result;
};

my $xc = XML::LibXML::XPathContext-&gt;new($node);
$xc-&gt;registerFunction('grep_nodes', \&amp;grep_nodes);
my @nodes = $xc-&gt;findnodes('//section[grep_nodes(para,"\bsearch(ing|es)?\b")]');</programlisting>
      </sect2>
      <sect2>
        <title>Variables</title>
<para>This example demonstrates <function>registerVarLookup()</function>
method. We use XPath variables to recycle results of previous evaluations:</para>
	<programlisting>sub var_lookup {
  my ($varname,$ns,$data)=@_;
  return $data-&gt;{$varname};
}

my $areas = XML::LibXML-&gt;new-&gt;parse_file('areas.xml');
my $empl = XML::LibXML-&gt;new-&gt;parse_file('employees.xml');

my $xc = XML::LibXML::XPathContext-&gt;new($empl);

my %variables = (
  A =&gt; $xc-&gt;find('/employees/employee[@salary&gt;10000]'),
  B =&gt; $areas-&gt;find('/areas/area[district='Brooklyn']/street'),
);

# get names of employees from $A working in an area listed in $B
$xc-&gt;registerVarLookupFunc(\&amp;var_lookup, \%variables);
my @nodes = $xc-&gt;findnodes('$A[work_area/street = $B]/name');
</programlisting>
      </sect2>
    </sect1>
    <sect1>
      <title>Methods</title>
      <variablelist>
        <varlistentry>
          <term>new</term>
          <listitem>
	    <funcsynopsis><funcsynopsisinfo>my $xpc = XML::LibXML::XPathContext-&gt;new();</funcsynopsisinfo></funcsynopsis>
            <para>Creates a new XML::LibXML::XPathContext object
            without a context node.</para>
	    <funcsynopsis><funcsynopsisinfo>my $xpc = XML::LibXML::XPathContext-&gt;new($node);</funcsynopsisinfo></funcsynopsis>
            <para>Creates a new XML::LibXML::XPathContext object with
            the context node set to <literal>$node</literal>.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>registerNs</term>
          <listitem><funcsynopsis><funcsynopsisinfo>$xpc-&gt;registerNs($prefix, $namespace_uri)</funcsynopsisinfo></funcsynopsis>
            <para>Registers namespace <literal>$prefix</literal> to
            <literal>$namespace_uri</literal>.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>unregisterNs</term>
          <listitem><funcsynopsis><funcsynopsisinfo>$xpc-&gt;unregisterNs($prefix)</funcsynopsisinfo></funcsynopsis>
            <para>Unregisters namespace <literal>$prefix</literal>.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>lookupNs</term>
          <listitem><funcsynopsis><funcsynopsisinfo>$uri = $xpc-&gt;lookupNs($prefix)</funcsynopsisinfo></funcsynopsis>
            <para>Returns namespace URI registered with
            <literal>$prefix</literal>. If <literal>$prefix</literal>
            is not registered to any namespace URI returns
            <literal>undef</literal>.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>registerVarLookupFunc</term>
          <listitem><funcsynopsis><funcsynopsisinfo>$xpc-&gt;registerVarLookupFunc($callback, $data)</funcsynopsisinfo></funcsynopsis>
            <para>Registers variable lookup function
	      <literal>$prefix</literal>. The registered function is
	      executed by the XPath engine each time an XPath variable
	      is evaluated. It takes three arguments:
	      <literal>$data</literal>, variable name, and variable
	      ns-URI and must return one value: a number or string or
	      any <literal>XML::LibXML::</literal> object that can be a result
	      of findnodes: Boolean, Literal, Number, Node
	      (e.g. Document, Element, etc.), or NodeList. For
	      convenience, simple (non-blessed) array references
	      containing only <xref linkend="XML-LibXML-Node"/> objects can be
	      used instead of an <olink targetdoc="XML::LibXML::NodeList">XML::LibXML::NodeList</olink>.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>getVarLookupData</term>
          <listitem>
	    <funcsynopsis><funcsynopsisinfo>$data = $xpc-&gt;getVarLookupData();</funcsynopsisinfo></funcsynopsis>
            <para>
	      Returns the data that have been associated with a
	      variable lookup function during a previous call to
	      <literal>registerVarLookupFunc</literal>.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>getVarLookupFunc</term>
          <listitem>
	    <funcsynopsis><funcsynopsisinfo>$callback = $xpc-&gt;getVarLookupFunc();</funcsynopsisinfo></funcsynopsis>
            <para>
	      Returns the variable lookup function previously registered with
	      <literal>registerVarLookupFunc</literal>.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>unregisterVarLookupFunc</term>
          <listitem>
	    <funcsynopsis><funcsynopsisinfo>$xpc-&gt;unregisterVarLookupFunc($name);</funcsynopsisinfo></funcsynopsis>
            <para>Unregisters variable lookup function and the associated lookup data.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>registerFunctionNS</term>
          <listitem><funcsynopsis><funcsynopsisinfo>$xpc-&gt;registerFunctionNS($name, $uri, $callback)</funcsynopsisinfo></funcsynopsis>
            <para>Registers an extension function
	      <literal>$name</literal> in <literal>$uri</literal>
	      namespace. <literal>$callback</literal> must be a CODE
	      reference. The arguments of the callback function are
	      either simple scalars or <literal>XML::LibXML::*</literal> objects
	      depending on the XPath argument types. The function is
	      responsible for checking the argument number and
	      types. Result of the callback code must be a single
	      value of the following types: a simple scalar
	      (number, string) or an arbitrary <literal>XML::LibXML::*</literal>
	      object that can be a result of findnodes: Boolean,
	      Literal, Number, Node (e.g. Document, Element, etc.), or
	      NodeList. For convenience, simple (non-blessed) array
	      references containing only <xref linkend="XML-LibXML-Node"/>
	      objects can be used instead of a
	      <olink targetdoc="XML::LibXML::NodeList">XML::LibXML::NodeList</olink>.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>unregisterFunctionNS</term>
          <listitem><funcsynopsis><funcsynopsisinfo>$xpc-&gt;unregisterFunctionNS($name, $uri)</funcsynopsisinfo></funcsynopsis>
            <para>
	      Unregisters extension function <literal>$name</literal>
	      in <literal>$uri</literal> namespace. Has the same
	      effect as passing <literal>undef</literal> as
	      <literal>$callback</literal> to
	      registerFunctionNS.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>registerFunction</term>
          <listitem><funcsynopsis><funcsynopsisinfo>$xpc-&gt;registerFunction($name, $callback)</funcsynopsisinfo></funcsynopsis>
            <para>Same as <literal>registerFunctionNS</literal> but
            without a namespace.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>unregisterFunction</term>
          <listitem><funcsynopsis><funcsynopsisinfo>$xpc-&gt;unregisterFunction($name)</funcsynopsisinfo></funcsynopsis>
            <para>Same as <literal>unregisterFunctionNS</literal> but
	      without a namespace.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>findnodes</term>
          <listitem><funcsynopsis><funcsynopsisinfo>@nodes = $xpc-&gt;findnodes($xpath)</funcsynopsisinfo></funcsynopsis>
          <funcsynopsis><funcsynopsisinfo>@nodes = $xpc-&gt;findnodes($xpath, $context_node )</funcsynopsisinfo></funcsynopsis>
          <funcsynopsis><funcsynopsisinfo>$nodelist = $xpc-&gt;findnodes($xpath, $context_node )</funcsynopsisinfo></funcsynopsis>
            <para>Performs the xpath statement on the current node and
	      returns the result as an array. In scalar context,
	      returns an <olink targetdoc="XML::LibXML::NodeList">XML::LibXML::NodeList</olink> object. Optionally, a
	      node may be passed as a second argument to set the
	      context node for the query.</para>
          <para>The xpath expression can be passed either as a string, or
	  as a  <olink targetdoc="XML::LibXML::XPathExpression">XML::LibXML::XPathExpression</olink> object.
	  </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>find</term>
          <listitem><funcsynopsis><funcsynopsisinfo>$object = $xpc-&gt;find($xpath )</funcsynopsisinfo></funcsynopsis>
          <funcsynopsis><funcsynopsisinfo>$object = $xpc-&gt;find($xpath, $context_node )</funcsynopsisinfo></funcsynopsis>
            <para>Performs the xpath expression using the current node
	      as the context of the expression, and returns the result
	      depending on what type of result the XPath expression
	      had. For example, the XPath <literal>1 * 3 +
	      52</literal> results in an <olink targetdoc="XML::LibXML::Number">XML::LibXML::Number</olink> object
	      being returned. Other expressions might return a
	      <olink targetdoc="XML::LibXML::Boolean">XML::LibXML::Boolean</olink> object, or a
	      <olink targetdoc="XML::LibXML::Literal">XML::LibXML::Literal</olink> object (a string). Each of those
	      objects uses Perl's overload feature to ``do the right
	      thing'' in different contexts. Optionally, a node may be
	      passed as a second argument to set the context node for
	      the query.</para>
          <para>The xpath expression can be passed either as a string, or
	  as a  <olink targetdoc="XML::LibXML::XPathExpression">XML::LibXML::XPathExpression</olink> object.
	  </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>findvalue</term>
          <listitem><funcsynopsis><funcsynopsisinfo>$value = $xpc-&gt;findvalue($xpath )</funcsynopsisinfo></funcsynopsis>
          <funcsynopsis><funcsynopsisinfo>$value = $xpc-&gt;findvalue($xpath, $context_node )</funcsynopsisinfo></funcsynopsis>
            <para>Is exactly equivalent to:</para>
	    <programlisting>$xpc-&gt;find( $xpath, $context_node )-&gt;to_literal;</programlisting>
            <para>That is, it returns the literal value of the
            results. This enables you to ensure that you get a string
            back from your search, allowing certain shortcuts. This
            could be used as the equivalent of &lt;xsl:value-of
            select=``some_xpath''/&gt;. Optionally, a node may be
            passed in the second argument to set the context node for
            the query.</para>
          <para>The xpath expression can be passed either as a string, or
	  as a  <olink targetdoc="XML::LibXML::XPathExpression">XML::LibXML::XPathExpression</olink> object.
	  </para>
          </listitem>
        </varlistentry>
	<varlistentry>
	  <term>exists</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$bool = $xpc-&gt;exists( $xpath_expression, $context_node );</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>This method behaves like <emphasis>findnodes</emphasis>, except
	    that it only returns a boolean value (1 if the expression matches a node, 0 otherwise)
	    and may be faster than <emphasis>findnodes</emphasis>, because
	    the XPath evaluation may stop early on the first match (this is true for libxml2 >= 2.6.27).
	    </para><para>For XPath expressions that do not return node-set,
	    the method returns true if the returned value is a non-zero number or a non-empty string.</para>
	  </listitem>
	</varlistentry>
        <varlistentry>
          <term>setContextNode</term>
          <listitem><funcsynopsis><funcsynopsisinfo>$xpc-&gt;setContextNode($node)</funcsynopsisinfo></funcsynopsis>
            <para>Set the current context node.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>getContextNode</term>
          <listitem>
	    <funcsynopsis><funcsynopsisinfo>my $node = $xpc-&gt;getContextNode;</funcsynopsisinfo></funcsynopsis>
            <para>Get the current context node.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>setContextPosition</term>
          <listitem><funcsynopsis><funcsynopsisinfo>$xpc-&gt;setContextPosition($position)</funcsynopsisinfo></funcsynopsis>
            <para>
	      Set the current context position. By default, this
	      value is -1 (and evaluating XPath function
	      <literal>position()</literal> in the initial context
	      raises an XPath error), but can be set to any value up
	      to context size. This usually only serves to cheat the
	      XPath engine to return given position when
	      <literal>position()</literal> XPath function is
	      called. Setting this value to -1 restores the default
	      behavior.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>getContextPosition</term>
          <listitem>
	    <funcsynopsis><funcsynopsisinfo>my $position = $xpc-&gt;getContextPosition;</funcsynopsisinfo></funcsynopsis>
            <para>Get the current context position.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>setContextSize</term>
          <listitem><funcsynopsis><funcsynopsisinfo>$xpc-&gt;setContextSize($size)</funcsynopsisinfo></funcsynopsis>
            <para>
	      Set the current context size. By default, this value is -1 (and
	      evaluating XPath function <literal>last()</literal> in
	      the initial context raises an XPath error), but can be
	      set to any non-negative value. This usually only serves
	      to cheat the XPath engine to return the given value when
	      <literal>last()</literal> XPath function is called. If
	      context size is set to 0, position is automatically also
	      set to 0. If context size is positive, position is
	      automatically set to 1. Setting context size to -1
	      restores the default behavior.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>getContextSize</term>
          <listitem>
	    <funcsynopsis><funcsynopsisinfo>my $size = $xpc-&gt;getContextSize;</funcsynopsisinfo></funcsynopsis>
            <para>Get the current context size.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>setContextNode</term>
          <listitem><funcsynopsis><funcsynopsisinfo>$xpc-&gt;setContextNode($node)</funcsynopsisinfo></funcsynopsis>
            <para>Set the current context node.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </sect1>
    <sect1>
      <title>Bugs And Caveats</title>
      <para>
	XML::LibXML::XPathContext objects
	<emphasis>are</emphasis> reentrant, meaning that you can call
	methods of an XML::LibXML::XPathContext even from XPath
	extension functions registered with the same object or from a
	variable lookup function. On the other hand, you should rather
	avoid registering new extension functions, namespaces and a
	variable lookup function from within extension functions and a
	variable lookup function, unless you want to experience
	untested behavior.
      </para>
    </sect1>
    <sect1>
      <title>Authors</title>
      <para>Ilya Martynov and Petr Pajas, based on
	XML::LibXML and XML::LibXSLT code by Matt Sergeant and
	Christian Glahn.</para>
    </sect1>
    <sect1>
      <title>Historical remark</title>
      <para>Prior to XML::LibXML 1.61 this module was distributed separately
	for maintenance reasons.
      </para>
    </sect1>
  </chapter>
  <chapter id="XML-LibXML-Reader">
    <title>XML::LibXML::Reader - interface to libxml2 pull parser</title>
    <titleabbrev>XML::LibXML::Reader</titleabbrev>
    <sect1>
      <title>Synopsis</title>
      <programlisting>use XML::LibXML::Reader;</programlisting>
      <programlisting>my $reader = XML::LibXML::Reader-&gt;new(location =&gt; "file.xml")
       or die "cannot read file.xml\n";
while ($reader-&gt;read) {
  processNode($reader);
}</programlisting>
      <programlisting>
sub processNode {
    my $reader = shift;
    printf "%d %d %s %d\n", ($reader-&gt;depth,
                             $reader-&gt;nodeType,
                             $reader-&gt;name,
                             $reader-&gt;isEmptyElement);
}
</programlisting>
      <para>or</para>
      <programlisting>
  my $reader = XML::LibXML::Reader-&gt;new(location =&gt; "file.xml")
       or die "cannot read file.xml\n";
  $reader-&gt;preservePattern('//table/tr');
  $reader-&gt;finish;
  print $reader-&gt;document-&gt;toString(1);
</programlisting>
    </sect1>
    <sect1>
      <title>DESCRIPTION</title>
      <para>This is a perl interface to libxml2's pull-parser implementation
	xmlTextReader
	<emphasis>http://xmlsoft.org/html/libxml-xmlreader.html</emphasis>.
	This feature requires at least libxml2-2.6.21.
	Pull-parsers (such as StAX in Java, or XmlReader in C#) use an iterator
	approach to parse XML documents. They are easier to program than
	event-based parser (SAX) and much more lightweight than
	tree-based parser (DOM), which load the complete tree into
	memory.</para>
      <para>The Reader acts as a cursor going forward on the document
	stream and stopping at each node on the way. At every point,
	the DOM-like methods of the Reader object allow one to examine the
	current node (name, namespace, attributes, etc.)</para>
      <para>The user's code keeps control of the progress and simply
	calls the <literal>read()</literal> function repeatedly to
	progress to the next node in the document order. Other
	functions provide means for skipping complete sub-trees, or
	nodes until a specific element, etc.</para>
      <para>At every time, only a very limited portion of the
	document is kept in the memory, which makes the API more
	memory-efficient than using DOM. However, it is also possible
	to mix Reader with DOM. At every point the user may copy the
	current node (optionally expanded into a complete sub-tree)
	from the processed document to another DOM tree, or to
	instruct the Reader to collect sub-document in form of a DOM
	tree consisting of selected nodes.</para>
      <para>Reader API also supports namespaces, xml:base, entity
	handling, and DTD validation. Schema and RelaxNG validation
	support will probably be added in some later revision of the
	Perl interface.</para>
      <para>The naming of methods compared to libxml2 and C#
	XmlTextReader has been changed slightly to match the
	conventions of XML::LibXML. Some functions have been changed
	or added with respect to the C interface.</para>
    </sect1>
    <sect1>
      <title>CONSTRUCTOR</title>
      <para>Depending on the XML source, the Reader object can be created with either of:</para>
      <programlisting>
  my $reader = XML::LibXML::Reader-&gt;new( location =&gt; "file.xml", ... );
  my $reader = XML::LibXML::Reader-&gt;new( string =&gt; $xml_string, ... );
  my $reader = XML::LibXML::Reader-&gt;new( IO =&gt; $file_handle, ... );
  my $reader = XML::LibXML::Reader-&gt;new( FD =&gt; fileno(STDIN), ... );
  my $reader = XML::LibXML::Reader-&gt;new( DOM =&gt; $dom, ... );
</programlisting>
      <para>where ... are (optional) reader options described below in <xref linkend="reader-parsing-options"/>
	or various parser options described in <xref linkend="XML-LibXML-Parser"/>.
	The constructor recognizes the following XML sources:</para>
      <sect2>
        <title>Source specification</title>
        <variablelist>
          <varlistentry>
            <term>location</term>
            <listitem>
              <para>Read XML from a local file or URL.</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>string</term>
            <listitem>
              <para>Read XML from a string.</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>IO</term>
            <listitem>
              <para>Read XML a Perl IO filehandle.</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>FD</term>
            <listitem>
              <para>Read XML from a file descriptor (bypasses Perl I/O
		layer, only applicable to filehandles for regular
		files or pipes). Possibly faster than IO.</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>DOM</term>
            <listitem>
              <para>Use reader API to walk through a pre-parsed
		<xref linkend="XML-LibXML-Document"/>.</para>
            </listitem>
          </varlistentry>
        </variablelist>
      </sect2>
      <sect2 id="reader-parsing-options">
        <title>Reader options</title>
        <variablelist>
          <varlistentry>
            <term>encoding => $encoding</term>
            <listitem>
              <para>override document encoding.</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>RelaxNG => $rng_schema</term>
            <listitem>
              <para>can be used to pass either a <xref linkend="XML-LibXML-RelaxNG"/>
		object or a filename or URL of a RelaxNG schema to the
		constructor. The schema is then used to validate the
		document as it is processed.</para>
            </listitem>
          </varlistentry>
          <varlistentry>
            <term>Schema => $xsd_schema</term>
            <listitem>
              <para>can be used to pass either a <xref linkend="XML-LibXML-Schema"/>
		object or a filename or URL of a W3C XSD schema to the
		constructor. The schema is then used to validate the
		document as it is processed.</para>
            </listitem>
          </varlistentry>
	  <varlistentry>
            <term>...</term>
            <listitem>
              <para>the reader further supports various
	      parser options described in
	      <xref linkend="XML-LibXML-Parser"/> (specifically those
	      labeled by /reader/).
	      </para>
            </listitem>
          </varlistentry>
	</variablelist>
      </sect2>
    </sect1>
    <sect1>
      <title>METHODS CONTROLLING PARSING PROGRESS</title>
<variablelist>
        <varlistentry>
          <term>read ()</term>
          <listitem>
            <para>Moves the position to the next node in the stream,
	      exposing its properties.</para>
            <para>Returns 1 if the node was read successfully, 0 if
	      there is no more nodes to read, or -1 in case of
	      error</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>readAttributeValue ()</term>
          <listitem>
            <para>Parses an attribute value into one or more Text and
	      EntityReference nodes.</para>
            <para>Returns 1 in case of success, 0 if the reader was not positioned on an attribute node or all the attribute values have been read, or -1 in case of error.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>readState ()</term>
          <listitem>
            <para>Gets the read state of the reader. Returns the state
	      value, or -1 in case of error. The module exports
	      constants for the Reader states, see STATES
	      below.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>depth ()</term>
          <listitem>
            <para>The depth of the node in the tree, starts at 0 for
	      the root node.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>next ()</term>
          <listitem>
            <para>Skip to the node following the current one in the
	      document order while avoiding the sub-tree if any.
	      Returns 1 if the node was read successfully, 0 if there
	      is no more nodes to read, or -1 in case of error.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>nextElement (localname?,nsURI?)</term>
          <listitem>
            <para>Skip nodes following the current one in the document
	      order until a specific element is reached. The element's
	      name must be equal to a given localname if defined, and
	      its namespace must equal to a given nsURI if defined.
	      Either of the arguments can be undefined (or omitted, in
	      case of the latter or both).</para>
            <para>Returns 1 if the element was found, 0 if there is no more nodes to read, or -1 in case of error.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>nextPatternMatch (compiled_pattern)</term>
          <listitem>
            <para>Skip nodes following the current one in the document
	      order until an element matching a given
	      compiled pattern is reached. See
              <xref linkend="XML-LibXML-Pattern"/> for information on
	      compiled patterns. See also the <literal>matchesPattern</literal>
	      method.</para>
            <para>Returns 1 if the element was found, 0 if there is no more nodes to read, or -1 in case of error.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>skipSiblings ()</term>
          <listitem>
            <para>Skip all nodes on the same or lower level until the
	      first node on a higher level is reached. In particular,
	      if the current node occurs in an element, the reader
	      stops at the end tag of the parent element, otherwise it
	      stops at a node immediately following the parent
	      node.</para>
            <para>Returns 1 if successful, 0 if end of the document is reached, or -1 in case of error.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>nextSibling ()</term>
          <listitem>
            <para>It skips to the node following the current one in
	      the document order while avoiding the sub-tree if
	      any.</para>
            <para>Returns 1 if the node was read successfully, 0 if
	      there is no more nodes to read, or -1 in case of
	      error</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>nextSiblingElement (name?,nsURI?)</term>
          <listitem>
            <para>Like nextElement but only processes sibling elements
	      of the current node (moving forward using
	      <literal>nextSibling ()</literal>  rather than
	      <literal>read ()</literal>,  internally).</para>
            <para>Returns 1 if the element was found, 0 if there is no
	      more sibling nodes, or -1 in case of error.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>finish ()</term>
          <listitem>
            <para>Skip all remaining nodes in the document, reaching end of the document.</para>
            <para>Returns 1 if successful, 0 in case of error.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>close ()</term>
          <listitem>
            <para>This method releases any resources allocated by the
	      current instance and closes any underlying input. It
	      returns 0 on failure and 1 on success. This method is
	      automatically called by the destructor when the reader
	      is forgotten, therefore you do not have to call it
	      directly.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </sect1>
    <sect1>
      <title>METHODS EXTRACTING INFORMATION</title>
<variablelist>
        <varlistentry>
          <term>name ()</term>
          <listitem>
            <para>Returns the qualified name of the current node, equal to (Prefix:)LocalName.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>nodeType ()</term>
          <listitem>
            <para>Returns the type of the current node. See NODE TYPES below.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>localName ()</term>
          <listitem>
            <para>Returns the local name of the node.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>prefix ()</term>
          <listitem>
            <para>Returns the prefix of the namespace associated with the node.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>namespaceURI ()</term>
          <listitem>
            <para>Returns the URI defining the namespace associated with the node.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>isEmptyElement ()</term>
          <listitem>
            <para>Check if the current node is empty, this is a bit
	      bizarre in the sense that &lt;a/&gt; will be considered
	      empty while &lt;a&gt;&lt;/a&gt; will not.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>hasValue ()</term>
          <listitem>
            <para>Returns true if the node can have a text value.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>value ()</term>
          <listitem>
            <para>Provides the text value of the node if present or undef if not available.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>readInnerXml ()</term>
          <listitem>
            <para>Reads the contents of the current node, including
	      child nodes and markup. Returns a string containing the
	      XML of the node's content, or undef if the current node
	      is neither an element nor attribute, or has no child
	      nodes.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>readOuterXml ()</term>
          <listitem>
            <para>Reads the contents of the current node, including
	      child nodes and markup.</para>
            <para>Returns a string containing the XML of the node
	      including its content, or undef if the current node is
	      neither an element nor attribute.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>nodePath()</term>
          <listitem>
            <para>Returns a canonical location path to the current element
	    from the root node to the current node. Namespaced
	    elements are matched by '*', because there is no way to declare
	    prefixes within XPath patterns. Unlike
	    <literal>XML::LibXML::Node::nodePath()</literal>, this function
	    does not provide sibling counts (i.e. instead of e.g. '/a/b[1]' and '/a/b[2]'
	    you get '/a/b' for both matches).
	    </para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>matchesPattern(compiled_pattern)</term>
          <listitem>
            <para>Returns a true value if the current
	    node matches a compiled pattern.
            See <xref linkend="XML-LibXML-Pattern"/> for information on
	    compiled patterns. See also the <literal>nextPatternMatch</literal>
	    method.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </sect1>
    <sect1>
      <title>METHODS EXTRACTING DOM NODES</title>
<variablelist>
        <varlistentry>
          <term>document ()</term>
          <listitem>
            <para>Provides access to the document tree built by the
	      reader. This function can be used to collect the
	      preserved nodes (see <literal>preserveNode()</literal>
	      and preservePattern).</para>
            <para>CAUTION: Never use this function to modify the tree
	      unless reading of the whole document is
	      completed!</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>copyCurrentNode (deep)</term>
          <listitem>
            <para>This function is similar a DOM function
	      <literal>copyNode()</literal>. It returns a copy of the
	      currently processed node as a corresponding DOM object.
	      Use deep = 1 to obtain the full sub-tree.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>preserveNode ()</term>
          <listitem>
            <para>This tells the XML Reader to preserve the current
	      node in the document tree. A document tree consisting of
	      the preserved nodes and their content can be obtained
	      using the method <literal>document()</literal> once
	      parsing is finished.</para>
            <para>Returns the node or NULL in case of error.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>preservePattern (pattern,\%ns_map)</term>
          <listitem>
            <para>This tells the XML Reader to preserve all nodes
	      matched by the pattern (which is a streaming XPath
	      subset). A document tree consisting of the preserved
	      nodes and their content can be obtained using the method
	      <literal>document()</literal> once parsing is
	      finished.</para>
            <para>An optional second argument can be used to provide a
	      HASH reference mapping prefixes used by the XPath to
	      namespace URIs.</para>
            <para>The XPath subset available with this function is
	      described at</para>
            <programlisting>http://www.w3.org/TR/xmlschema-1/#Selector</programlisting>
            <para>and matches the production</para>
            <programlisting>Path ::= ('.//')? ( Step '/' )* ( Step | '@' NameTest )</programlisting>
            <para>Returns a positive number in case of success and -1
	      in case of error</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </sect1>
    <sect1>
      <title>METHODS PROCESSING ATTRIBUTES</title>
<variablelist>
        <varlistentry>
          <term>attributeCount ()</term>
          <listitem>
            <para>Provides the number of attributes of the current
	      node.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>hasAttributes ()</term>
          <listitem>
            <para>Whether the node has attributes.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>getAttribute (name)</term>
          <listitem>
            <para>Provides the value of the attribute with the
	      specified qualified name.</para>
            <para>Returns a string containing the value of the
	      specified attribute, or undef in case of error.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>getAttributeNs (localName, namespaceURI)</term>
          <listitem>
            <para>Provides the value of the specified
	      attribute.</para>
            <para>Returns a string containing the value of the
	      specified attribute, or undef in case of error.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>getAttributeNo (no)</term>
          <listitem>
            <para>Provides the value of the attribute with the
	      specified index relative to the containing
	      element.</para>
            <para>Returns a string containing the value of the
	      specified attribute, or undef in case of error.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>isDefault ()</term>
          <listitem>
            <para>Returns true if the current attribute node was
	      generated from the default value defined in the
	      DTD.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>moveToAttribute (name)</term>
          <listitem>
            <para>Moves the position to the attribute with the
	      specified local name and namespace URI.</para>
            <para>Returns 1 in case of success, -1 in case of error, 0
	      if not found</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>moveToAttributeNo (no)</term>
          <listitem>
            <para>Moves the position to the attribute with the
	      specified index relative to the containing
	      element.</para>
            <para>Returns 1 in case of success, -1 in case of error, 0
	      if not found</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>moveToAttributeNs (localName,namespaceURI)</term>
          <listitem>
            <para>Moves the position to the attribute with the
	      specified local name and namespace URI.</para>
            <para>Returns 1 in case of success, -1 in case of error, 0
	      if not found</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>moveToFirstAttribute ()</term>
          <listitem>
            <para>Moves the position to the first attribute associated
	      with the current node.</para>
            <para>Returns 1 in case of success, -1 in case of error, 0
	      if not found</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>moveToNextAttribute ()</term>
          <listitem>
            <para>Moves the position to the next attribute associated
	      with the current node.</para>
            <para>Returns 1 in case of success, -1 in case of error, 0
	      if not found</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>moveToElement ()</term>
          <listitem>
            <para>Moves the position to the node that contains the
	      current attribute node.</para>
            <para>Returns 1 in case of success, -1 in case of error, 0
	      if not moved</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>isNamespaceDecl ()</term>
          <listitem>
            <para>Determine whether the current node is a namespace
	      declaration rather than a regular attribute.</para>
            <para>Returns 1 if the current node is a namespace
	      declaration, 0 if it is a regular attribute or other
	      type of node, or -1 in case of error.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </sect1>
    <sect1>
      <title>OTHER METHODS</title>
<variablelist>
        <varlistentry>
          <term>lookupNamespace (prefix)</term>
          <listitem>
            <para>Resolves a namespace prefix in the scope of the
	      current element.</para>
            <para>Returns a string containing the namespace URI to
	      which the prefix maps or undef in case of error.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>encoding ()</term>
          <listitem>
            <para>Returns a string containing the encoding of the
	      document or undef in case of error.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>standalone ()</term>
          <listitem>
            <para>Determine the standalone status of the document
	      being read. Returns 1 if the document was declared to be
	      standalone, 0 if it was declared to be not standalone,
	      or -1 if the document did not specify its standalone
	      status or in case of error.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>xmlVersion ()</term>
          <listitem>
            <para>Determine the XML version of the document being
	      read. Returns a string containing the XML version of the
	      document or undef in case of error.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>baseURI ()</term>
          <listitem>
            <para>Returns the base URI of a given node.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>isValid ()</term>
          <listitem>
            <para>Retrieve the validity status from the parser.</para>
            <para>Returns 1 if valid, 0 if no, and -1 in case of
	      error.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>xmlLang ()</term>
          <listitem>
            <para>The xml:lang scope within which the node
	      resides.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>lineNumber ()</term>
          <listitem>
            <para>Provide the line number of the current parsing
	      point.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>columnNumber ()</term>
          <listitem>
            <para>Provide the column number of the current parsing
	      point.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>byteConsumed ()</term>
          <listitem>
            <para>This function provides the current index of the
	      parser relative to the start of the current entity. This
	      function is computed in bytes from the beginning
	      starting at zero and finishing at the size in bytes of
	      the file if parsing a file. The function is of constant
	      cost if the input is UTF-8 but can be costly if run on
	      non-UTF-8 input.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>setParserProp (prop =&gt; value, ...)</term>
          <listitem>
            <para>Change the parser processing behaviour by changing
	      some of its internal properties. The following
	      properties are available with this function:
	      ``load_ext_dtd'', ``complete_attributes'',
	      ``validation'', ``expand_entities''.</para>
            <para>Since some of the properties can only be changed
	      before any read has been done, it is best to set the
	      parsing properties at the constructor.</para>
            <para>Returns 0 if the call was successful, or -1 in case
	      of error</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>getParserProp (prop)</term>
          <listitem>
            <para>Get value of an parser internal property. The
	      following property names can be used: ``load_ext_dtd'',
	      ``complete_attributes'', ``validation'',
	      ``expand_entities''.</para>
            <para>Returns the value, usually 0 or 1, or -1 in case of
	      error.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </sect1>
    <sect1>
      <title>DESTRUCTION</title>
      <para>XML::LibXML takes care of the reader object destruction
	when the last reference to the reader object goes out of
	scope. The document tree is preserved, though, if either of
	$reader-&gt;document or $reader-&gt;preserveNode was used and
	references to the document tree exist.</para>
    </sect1>
    <sect1>
      <title>NODE TYPES</title>
      <para>The reader interface provides the following constants for
	node types (the constant symbols are exported by default or if
	tag <literal>:types</literal> is used).</para>
      <programlisting>XML_READER_TYPE_NONE                    =&gt; 0
XML_READER_TYPE_ELEMENT                 =&gt; 1
XML_READER_TYPE_ATTRIBUTE               =&gt; 2
XML_READER_TYPE_TEXT                    =&gt; 3
XML_READER_TYPE_CDATA                   =&gt; 4
XML_READER_TYPE_ENTITY_REFERENCE        =&gt; 5
XML_READER_TYPE_ENTITY                  =&gt; 6
XML_READER_TYPE_PROCESSING_INSTRUCTION  =&gt; 7
XML_READER_TYPE_COMMENT                 =&gt; 8
XML_READER_TYPE_DOCUMENT                =&gt; 9
XML_READER_TYPE_DOCUMENT_TYPE           =&gt; 10
XML_READER_TYPE_DOCUMENT_FRAGMENT       =&gt; 11
XML_READER_TYPE_NOTATION                =&gt; 12
XML_READER_TYPE_WHITESPACE              =&gt; 13
XML_READER_TYPE_SIGNIFICANT_WHITESPACE  =&gt; 14
XML_READER_TYPE_END_ELEMENT             =&gt; 15
XML_READER_TYPE_END_ENTITY              =&gt; 16
XML_READER_TYPE_XML_DECLARATION         =&gt; 17
</programlisting>
    </sect1>
    <sect1>
      <title>STATES</title>
      <para>The following constants represent the values returned by
	<literal>readState()</literal>. They are exported by default,
	or if tag <literal>:states</literal> is used:</para>
      <programlisting>XML_READER_NONE      =&gt; -1
XML_READER_START     =&gt;  0
XML_READER_ELEMENT   =&gt;  1
XML_READER_END       =&gt;  2
XML_READER_EMPTY     =&gt;  3
XML_READER_BACKTRACK =&gt;  4
XML_READER_DONE      =&gt;  5
XML_READER_ERROR     =&gt;  6
</programlisting>
    </sect1>
    <sect1>
      <title>SEE ALSO</title>
      <para><xref linkend="XML-LibXML-Pattern"/> for information about compiled patterns.</para>
      <para>http://xmlsoft.org/html/libxml-xmlreader.html</para>
      <para>http://dotgnu.org/pnetlib-doc/System/Xml/XmlTextReader.html</para>
    </sect1>
    <sect1>
      <title>ORIGINAL IMPLEMENTATION</title>
      <para>Heiko Klein, &lt;H.Klein@gmx.net&lt;gt&gt; and Petr Pajas</para>
    </sect1>
  </chapter>
  <chapter id="XML-LibXML-XPathExpression">
    <title>XML::LibXML::XPathExpression - interface to libxml2 pre-compiled XPath expressions</title>
    <titleabbrev>XML::LibXML::XPathExpression</titleabbrev>
    <sect1>
      <title>Synopsis</title>
      <programlisting>use XML::LibXML;
my $compiled_xpath = XML::LibXML::XPathExpression-&gt;new('//foo[@bar="baz"][position()&lt;4]');

# interface from XML::LibXML::Node

my $result = $node->find($compiled_xpath);
my @nodes = $node->findnodes($compiled_xpath);
my $value = $node->findvalue($compiled_xpath);

# interface from XML::LibXML::XPathContext

my $result = $xpc->find($compiled_xpath,$node);
my @nodes = $xpc->findnodes($compiled_xpath,$node);
my $value = $xpc->findvalue($compiled_xpath,$node);
</programlisting>
    </sect1>
    <sect1>
      <title>Description</title>
      <para>This is a perl interface to libxml2's pre-compiled XPath expressions.
      Pre-compiling an XPath expression can give in some performance
      benefit if the same XPath query is evaluated many times.
      <function>XML::LibXML::XPathExpression</function> objects
      can be passed to all <function>find...</function>
      functions <function>XML::LibXML</function>
      that expect an XPath expression.
      </para>
      <variablelist>
	<varlistentry>
	  <term>new()</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$compiled = XML::LibXML::XPathExpression-&gt;new( xpath_string );</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>The constructor takes an XPath 1.0 expression as a string
	    and returns an object representing the pre-compiled
	    expressions (the actual data structure is internal to libxml2).
	    </para>
	  </listitem>
	</varlistentry>
      </variablelist>
    </sect1>
  </chapter>
  <chapter id="XML-LibXML-Pattern">
    <title>XML::LibXML::Pattern - interface to libxml2 XPath patterns</title>
    <titleabbrev>XML::LibXML::Pattern</titleabbrev>
    <sect1>
      <title>Synopsis</title>
      <programlisting>use XML::LibXML;
my $pattern = XML::LibXML::Pattern-&gt;new('/x:html/x:body//x:div', { 'x' => 'http://www.w3.org/1999/xhtml' });
# test a match on an XML::LibXML::Node $node

if ($pattern->matchesNode($node)) { ... }

# or on an XML::LibXML::Reader

if ($reader->matchesPattern($pattern)) { ... }

# or skip reading all nodes that do not match

print $reader->nodePath while $reader->nextPatternMatch($pattern);
</programlisting>
    </sect1>
    <sect1>
      <title>Description</title>
      <para>This is a perl interface to libxml2's pattern matching support
	<emphasis>http://xmlsoft.org/html/libxml-pattern.html</emphasis>.
      This feature requires recent versions of libxml2.</para>
      <para>Patterns are a small subset of XPath language, which is limited
      to (disjunctions of) location paths involving the child and descendant axes in abbreviated form
      as described by the extended BNF given below:
      </para>
      <programlisting>Selector ::=     Path ( '|' Path )*
Path     ::=     ('.//' | '//' | '/' )? Step ( '/' Step )*
Step     ::=     '.' | NameTest
NameTest ::=     QName | '*' | NCName ':' '*'</programlisting>
      <para>For readability, whitespace may be used in selector XPath expressions even though not explicitly allowed by the grammar: whitespace may be freely added within patterns before or after any token, where</para>
      <programlisting>token     ::=     '.' | '/' | '//' | '|' | NameTest</programlisting>
      <para>Note that no predicates or attribute tests are allowed.</para>
      <para>Patterns are particularly useful for stream parsing provided via the <literal>XML::LibXML::Reader</literal> interface.</para>
      <variablelist>
	<varlistentry>
	  <term>new()</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$pattern = XML::LibXML::Pattern-&gt;new( pattern, { prefix => namespace_URI, ... } );</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>The constructor of a pattern takes a pattern expression (as described
	    by the BNF grammar above) and an optional HASH reference mapping
	    prefixes to namespace URIs. The method returns a compiled pattern object.
	    </para>
	    <para>
	    Note that if the document
	    has a default namespace, it must still be given an prefix in order
	    to be matched (as demanded by the XPath 1.0 specification). For example,
	    to match an element <literal>&lt;a xmlns="http://foo.bar"&lt;/a></literal>, one
	    should use a pattern like this:
	    </para>
	    <programlisting>$pattern = XML::LibXML::Pattern-&gt;new( 'foo:a', { foo => 'http://foo.bar' });</programlisting>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>matchesNode($node)</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$bool = $pattern->matchesNode($node);</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>Given an XML::LibXML::Node object, returns a true value if
	    the node is matched by the compiled pattern expression.</para>
	  </listitem>
	</varlistentry>
      </variablelist>
    </sect1>
    <sect1>
      <title>SEE ALSO</title>
      <para><xref linkend="XML-LibXML-Reader"/> for other methods involving compiled patterns.</para>
    </sect1>
  </chapter>
  <chapter id="XML-LibXML-RegExp">
    <title>XML::LibXML::RegExp - interface to libxml2 regular expressions</title>
    <titleabbrev>XML::LibXML::RegExp</titleabbrev>
    <sect1>
      <title>Synopsis</title>
      <programlisting>use XML::LibXML;
my $compiled_re = XML::LibXML::RegExp-&gt;new('[0-9]{5}(-[0-9]{4})?');
if ($compiled_re->isDeterministic()) { ... }
if ($compiled_re->matches($string)) { ... }
</programlisting>
    </sect1>
    <sect1>
      <title>Description</title>
      <para>This is a perl interface to libxml2's implementation of regular expressions, which are used e.g. for validation of XML Schema simple types (pattern facet).</para>
      <variablelist>
	<varlistentry>
	  <term>new()</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$compiled_re = XML::LibXML::RegExp-&gt;new( $regexp_str );</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>The constructor takes a string containing a regular expression
	    and returns a compiled regexp object.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>matches($string)</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$bool = $compiled_re->matches($string);</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>Given a string value, returns a true value if
	    the value is matched by the compiled regular expression.</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>isDeterministic()</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$bool = $compiled_re->isDeterministic();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>Returns a true value if the regular expression is deterministic; returns false otherwise. (See the definition of determinism in the <ulink url="http://www.w3.org/TR/REC-xml/#determinism">XML spec</ulink>)</para>
	  </listitem>
	</varlistentry>
      </variablelist>
    </sect1>
  </chapter>
    <chapter id="XML-LibXML-NamedNodeMap">
        <title>A map for named nodes</title>

        <titleabbrev>XML::LibXML::NamedNodeMap</titleabbrev>
        <sect1>
            <title>Synopsis</title>
            <programlisting>use XML::LibXML;
my $map = XML::LibXML::NamedNodeMap->new(@nodes);

my $nodes_list = $map->nodes();

my $node_with_index_2 = $map->item(2);
            </programlisting>
        </sect1>
        <sect1>
            <title>Description</title>

        <para>XML::LibXML::NamedNodeMap maps nodes' names to nodes.</para>
	</sect1>
        <sect1>
            <title>Methods</title>

        <variablelist>
            <varlistentry>
                <term>length</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>my $length = $map-&gt;length;</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the number of nodes in the map.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>nodes</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>my $nodes_ref = $node->nodes()</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns a reference to the list of nodes.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>item</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>my $node_2 = $map->item(2);</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the node with the index of the argument
                    (starting from 0)</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>getNamedItem</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>my $node = $map->getNamedItem('phone_number');</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Returns the node with the name.</para>

                </listitem>
            </varlistentry>

            <varlistentry>
                <term>setNamedItem</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$map->setNamedItem($new_node)</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Sets the node with the same name as
                    <literal>$new_node</literal> to
                    <literal>$new_node</literal>.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>removeNamedItem</term>

                <listitem>
                    <funcsynopsis>
                        <funcsynopsisinfo>$map->removeNamedItem($name)</funcsynopsisinfo>
                    </funcsynopsis>

                    <para>Remove the item with the name
                    <literal>$name</literal>.</para>
                </listitem>
            </varlistentry>

            <varlistentry>
                <term>getNamedItemNS</term>

                <listitem><para>
                <emphasis>Not implemented yet.</emphasis>.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term>setNamedItemNS</term>

                <listitem><para>
                <emphasis>Not implemented yet.</emphasis>.
                </para></listitem>
            </varlistentry>
            <varlistentry>
                <term>removeNamedItemNS</term>

                <listitem><para>
                <emphasis>Not implemented yet.</emphasis>.
                </para></listitem>
            </varlistentry>
        </variablelist>
      </sect1>
    </chapter>
  <chapter id="XML-LibXML-Error">
    <title>Structured Errors</title>
    <titleabbrev>XML::LibXML::Error</titleabbrev>
    <sect1>
      <title>Synopsis</title>
      <programlisting>
        eval { ... };
        if (ref($@)) {
          # handle a structured error (XML::LibXML::Error object)
        } elsif ($@) {
          # error, but not an XML::LibXML::Error object
        } else {
          # no error
        }
      </programlisting>
    </sect1>
    <sect1>
      <title>Description</title>
      <para>The
	XML::LibXML::Error class is a tiny frontend to
	<emphasis>libxml2</emphasis>&#39;s structured error support. If
	XML::LibXML is compiled with structured error support, all errors
	reported by libxml2 are transformed to XML::LibXML::Error
	objects. These objects automatically serialize to the
	corresponding error messages when printed or used in a string
	operation, but as objects, can also be used to get a detailed and
	structured information about the error that occurred.
      </para>
      <para>Unlike most other XML::LibXML objects, XML::LibXML::Error
	doesn't wrap an underlying <emphasis>libxml2</emphasis>
	structure directly, but rather transforms it to a blessed Perl
	hash reference containing the individual fields of the
	structured error information as hash key-value pairs. Individual
	items (fields) of a structured error can either be
	obtained directly as $@-&#62;{field}, or using autoloaded
	methods such as $@-&#62;field() (where field is the field
	name). XML::LibXML::Error objects have the following fields:
	domain, code, level, file, line, nodename, message, str1, str2,
	str3, num1, num2, and _prev (some of them may be undefined).
      </para>
      <variablelist>
	<varlistentry>
	  <term>$XML::LibXML::Error::WARNINGS</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$XML::LibXML::Error::WARNINGS=1;</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>Traditionally, XML::LibXML was suppressing parser
	      warnings by setting libxml2's global variable
	      xmlGetWarningsDefaultValue to 0. Since
	      1.70 we do not change libxml2's global
	      variables anymore; for backward compatibility,
	      XML::LibXML suppresses warnings.
	      This variable can be set to 1
	      to enable reporting of these warnings via
	      Perl <literal>warn</literal>
	      and to 2 to report hem via <literal>die</literal>.
	    </para>
	  </listitem>
        </varlistentry>
        <varlistentry>
	  <term>as_string</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$message = $@-&#62;as_string();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>This function serializes an XML::LibXML::Error
	      object to a string containing the full error message
	      close to the message produced by <emphasis>libxml2</emphasis> default error
	      handlers and tools like xmllint. This method is also used
	      to overload "" operator on XML::LibXML::Error, so it is
	      automatically called whenever XML::LibXML::Error object
	      is treated as a string (e.g. in print $@).
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>dump</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>print $@->dump();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>This function serializes an XML::LibXML::Error to a
	      string displaying all fields of the error structure
	      individually on separate lines of the form 'name' => 'value'.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>domain</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$error_domain = $@->domain();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>Returns string containing information about what part
	      of the library raised the error. Can be one of:
	      "parser", "tree", "namespace", "validity", "HTML parser",
	      "memory", "output", "I/O", "ftp", "http",
	      "XInclude", "XPath", "xpointer", "regexp", "Schemas
	      datatype",
	      "Schemas parser", "Schemas validity",
	      "Relax-NG parser", "Relax-NG validity", "Catalog",
	      "C14N", "XSLT", "validity".
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>code</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$error_code = $@->code();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>Returns the actual libxml2 error code.
	      The XML::LibXML::ErrNo module defines
	      constants for individual error codes. Currently
	      libxml2 uses over 480 different error codes.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>message</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$error_message = $@->message();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>Returns a human-readable informative error
	      message.</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>level</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$error_level = $@->level();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>Returns an integer value describing how consequent is
	      the error. XML::LibXML::Error defines the following
	      constants:
	    </para>
	    <itemizedlist>
	      <listitem>
		<para>XML_ERR_NONE = 0</para>
	      </listitem>
	      <listitem>
		<para>XML_ERR_WARNING = 1 : A simple warning.</para>
	      </listitem>
	      <listitem>
		<para>XML_ERR_ERROR = 2 : A recoverable error.</para>
	      </listitem>
	      <listitem>
		<para>XML_ERR_FATAL = 3 : A fatal error.</para>
	      </listitem>
	    </itemizedlist>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>file</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$filename = $@->file();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>Returns the filename of the file being processed while
	      the error occurred.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>line</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$line = $@->line();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>The line number, if available.</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>nodename</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$nodename = $@->nodename();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>Name of the node where error occurred, if available.
	      When this field is non-empty, libxml2 actually returned a
	      physical pointer to the specified node. Due to memory
	      management issues, it is very difficult to implement a
	      way to expose the pointer to the Perl level as a
	      XML::LibXML::Node. For this reason, XML::LibXML::Error
	      currently only exposes the name the node.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>str1</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$error_str1 = $@->str1();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>Error specific. Extra string information.</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>str2</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$error_str2 = $@->str2();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>Error specific. Extra string information.</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>str3</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$error_str3 = $@->str3();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>Error specific. Extra string information.</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>num1</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$error_num1 = $@->num1();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>Error specific. Extra numeric information.</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>num2</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$error_num2 = $@->num2();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>In recent libxml2 versions, this
	    value contains a column number of the error or 0 if N/A.</para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>context</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$string = $@->context();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>For parsing errors, this field contains
	    about 80 characters of the XML near the place
	    where the error occurred. The field
	    <function>$@->column()</function>
	    contains the corresponding offset.
	    Where N/A, the field is undefined.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>column</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$offset = $@->column();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>See <function>$@->column()</function> above.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term>_prev</term>
	  <listitem>
	    <funcsynopsis>
	      <funcsynopsisinfo>$previous_error = $@->_prev();</funcsynopsisinfo>
	    </funcsynopsis>
	    <para>This field can possibly hold a reference to another
	      XML::LibXML::Error object representing an error which
	      occurred just before this error.</para>
	  </listitem>
	</varlistentry>
      </variablelist>
    </sect1>
  </chapter>
  <chapter id="XML-LibXML-ErrNo">
    <title>Structured Errors</title>
    <titleabbrev>XML::LibXML::ErrNo</titleabbrev>
    <sect1>
      <title>Description</title>
      <para>This module is based on xmlerror.h libxml2 C header file.
      It defines symbolic constants for all libxml2 error codes.
      Currently libxml2 uses over 480 different error codes.
      See also XML::LibXML::Error.
      </para>
    </sect1>
  </chapter>
  <chapter id="XML-LibXML-Common">
    <title>Constants and Character Encoding Routines</title>
    <titleabbrev>XML::LibXML::Common</titleabbrev>
    <sect1>
      <title>Synopsis</title>
      <programlisting>use XML::LibXML::Common;</programlisting>
    </sect1>
    <sect1>
      <title>Description</title>
      <para>
	XML::LibXML::Common defines constants for all node types
	and provides interface to libxml2 charset conversion
	functions.
      </para>
      <para>Since XML::LibXML use their own node type definitions,
      one may want to use XML::LibXML::Common in its compatibility
      mode:
      </para>
      <sect2>
	<title>Exporter TAGS</title>
	<programlisting>use XML::LibXML::Common qw(:libxml);</programlisting>
	<para><literal>:libxml</literal> tag will use the XML::LibXML Compatibility mode, which defines the
	old 'XML_' node-type definitions.</para>
	<programlisting>use XML::LibXML::Common qw(:gdome);</programlisting>
	<para><literal>:gdome</literal> tag will use the XML::GDOME Compatibility mode, which defines the
	old 'GDOME_' node-type definitions.</para>
	<programlisting>use XML::LibXML::Common qw(:w3c);</programlisting>
	<para>This uses the nodetype definition names as specified for DOM.</para>
	<programlisting>use XML::LibXML::Common qw(:encoding);</programlisting>
	<para>
	  This tag can be used to export only the charset encoding functions of XML::LibXML::Common.
	</para>
      </sect2>
      <sect2>
	<title>Exports</title>
	<para>
	  By default the W3 definitions as defined in the DOM specifications and
	  the encoding functions are exported by XML::LibXML::Common.
	</para>
      </sect2>
      <sect2>
	<title>Encoding functions</title>
	<para>
	  To encode or decode a string to or from UTF-8, XML::LibXML::Common exports
	  two functions, which provide an interface to the encoding support in <literal>libxml2</literal>.
	  Which encodings are supported by these functions depends
	  on how <literal>libxml2</literal> was compiled.  UTF-16 is
	  always supported and on most installations, ISO encodings are
	  supported as well.
	</para>
	<para>
	  This interface was useful for older versions of Perl.
	  Since Perl >= 5.8 provides similar functions via the <literal>Encode</literal> module,
	  it is probably a good idea to use those instead.
	</para>
	<variablelist>
	  <varlistentry>
	    <term>encodeToUTF8</term>
	    <listitem>
	      <funcsynopsis>
		<funcsynopsisinfo>$encodedstring = encodeToUTF8( $name_of_encoding, $sting_to_encode );</funcsynopsisinfo>
	      </funcsynopsis>
	      <para>The function will convert a byte string from the specified encoding to an UTF-8 encoded character string.</para>
	    </listitem>
	  </varlistentry>
	  <varlistentry>
	    <term>decodeToUTF8</term>
	    <listitem>
	      <funcsynopsis>
		<funcsynopsisinfo>$decodedstring = decodeFromUTF8($name_of_encoding, $string_to_decode );</funcsynopsisinfo>
	      </funcsynopsis>
	      <para>
		This function converts an UTF-8 encoded character string to a specified
		encoding. Note that the conversion can raise an error if the
		given string contains characters that cannot be represented in the target encoding.
	      </para>
	    </listitem>
	  </varlistentry>
	</variablelist>
	<para>Both these functions report their errors on the standard
	error. If an error occurs the function will croak(). To catch
	the error information it is required to call the encoding
	function from within an eval block in order to prevent the
	entire script from being stopped on encoding error.</para>
      </sect2>
      <sect2>
	<title>A note on history</title>
	<para>
	Before XML::LibXML 1.70, this class was available as a
	separate CPAN distribution, intended to provide functionality
	shared between XML::LibXML, XML::GDOME, and possibly other
	modules. Since there seems to be no progress in this
	direction, we decided to merge XML::LibXML::Common 0.13 and
	XML::LibXML 1.70 to one CPAN distribution.
	</para>
	<para>The merge also naturally eliminates a practical and
	urgent problem experienced by many XML::LibXML users on certain
	platforms, namely mysterious misbehavior of XML::LibXML
	occurring if the installed (often pre-packaged) version of
	XML::LibXML::Common was compiled against an older version of
	libxml2 than XML::LibXML.
      </para>
      </sect2>
    </sect1>
  </chapter>
</book>