=head1 NAME

XML::LibXML::DOM - XML::LibXML DOM Implementation


=head1 DESCRIPTION

XML::LibXML provides an lightwight interface to modify node of the document
tree generated by the XML::LibXML parser. This interface follows as far as
possible the DOM Level 3 specification. Additionally to the specified functions
the XML::LibXML supports some functions that are more handy to use in the perl
environment.

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 different than a perl hash or array. The only way to
access these structure's values is through the DOM interface provided by
XML::LibXML. This also means, that one can't simply inherit a XML::LibXML node
and add new member variables as they were hash keys.

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.
More it offers an simple way to build or modify documents that are created by
XML::LibXML's parser.

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.

One of the most important parts of the XML::LibXML DOM interface is, that the
interfaces try do follow the DOM Level 3 specification rather strict. This
means the interface functions are names as the DOM specification says and not
what widespread Java interfaces claim to be standard. Although there are
several functions that have only a singular interface that is conform to the
DOM spec XML::LibXML provides an additional Java style alias interface.

Also there are some function interfaces left over from early stages of
XML::LibXML for compatibility reasons. These interfaces are for compatibility
reasons only. They might disappear in one of the future versions of
XML::LibXML, so a user is requested to switch over the official functions.

More recent versions of perl (e.g. 5.6.1 or higher) support special flags to
disinguish between UTF8 and so called binary data. XML::LibXML provides for
these versions functionality to make efficient use of these flags: If a
document has set an encoding other than UTF8 all strings that are not already
in UTF8 are implicitly encoded from the document encoding to UTF8. On output
these strings are commonly returned as UTF8 unless a user does request
explicitly the original (aka. document) encoding.

Older version of perl (such as 5.00503 or less) do not support these flags. If
XML::LibXML is build for these versions, all strings have to get encoded to
UTF8 manualy before they are passed to any DOM functions.

NOTE: XML::LibXML's magic encoding may not work on all plattforms. Some
platforms are known to have a broken iconv(), which is partly used by libxml2.
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. If your document gets parsed with out causing any segmentation
faults, bus errors or whatever your OS throws. An example for such a test can
be found in test 19encoding.t of the distribution.

Namespaces and XML::LibXML's DOM implementation

XML::LibXML's DOM implementation follows the DOM implementation of libxml2.
This is important to know if namespaces are used. Namespaces cannot be declared
on an document node. This is basicly because XPath doesn't know about document
nodes. Therefore namespaces have to be declared on element nodes. This can
happen explicitly by using XML::LibXML:Element's setNamespace() function or
more or less implicitly by using XML::LibXML::Document's createElementNS() or
createAttributeNS() function. If the a namespace is not declared on the
documentElement, the namespace will be localy 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 in
internally applied to the attribute and later declared on the node the
attribute is appended to.

The following example may explain this a bit:

   my $doc = XML::LibXML->createDocument;
   my $root = $doc->createElementNS( "", "foo" );
   $doc->setDocumentElement( $root );
  
   my $attr = $doc->createAttributeNS( "bar", "bar:foo", "test" );
   $root->setAttributeNodeNS( $attr );               

This piece of code will result the following document:

   <?xml version="1.0"?>
   <foo xmlns:bar="bar" bar:foo="test"/>

Note that the namespace is declared on the document element while the
setAttributeNodeNS() call.

Here it is 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 never use setAttributeNode() but
setAttributeNodeNS().

=head1 AUTHORS

Matt Sergeant, 
Christian Glahn, 
=head1 VERSION

1.55

=head1 COPYRIGHT

2001-2002, AxKit.com Ltd; 2001-2003 Christian Glahn, All rights reserved.

=cut
