NAME

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

DESCRIPTION

       XML::LibXML provides an light-wight interface to modify a 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 an 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.  Moreover, 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 (<http://www.w3.org/TR/DOM-Level-3-Core/>)
       rather strictly. This means the interface functions are named 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 conforms 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 to the official functions.

   Encodings and XML::LibXML's DOM implementation
       See the section on Encodings in the XML::LibXML manual page.

   Namespaces and XML::LibXML's DOM implementation
       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.

       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.

       This is both inconvenient, causes problems in serialization of DOM to XML, and most
       importantly, seems almost impossible to implement over libxml2.

       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.

       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.

       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.

       Namespace declarations are also created when 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).

       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 in the following document:

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

       The namespace is declared on the document element during the setAttributeNodeNS() call.

       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).

       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 never use setAttribute() but setAttributeNS().

AUTHORS

       Matt Sergeant, Christian Glahn, Petr Pajas

VERSION

       2.0108

COPYRIGHT

       2001-2007, AxKit.com Ltd.

       2002-2006, Christian Glahn.

       2006-2009, Petr Pajas.