=head1 NAME

XML::DOM::DocumentType - An XML document type (DTD) in XML::DOM

=head1 DESCRIPTION

XML::DOM::DocumentType extends L<XML::DOM::Node>.

Each Document has a doctype attribute whose value is either null or a
DocumentType object. The DocumentType interface in the DOM Level 1 Core
provides an interface to the list of entities that are defined for the
document, and little else because the effect of namespaces and the
various XML scheme efforts on DTD representation are not clearly
understood as of this writing. 
The DOM Level 1 doesn't support editing DocumentType nodes.

B<Not In DOM Spec>: This implementation has added a lot of extra 
functionality to the DOM Level 1 interface. 
To allow editing of the DocumentType nodes, see XML::DOM::ignoreReadOnly.

=head2 METHODS

=over 4

=item getName

Returns the name of the DTD, i.e. the name immediately following the
DOCTYPE keyword.

=item getEntities

A NamedNodeMap containing the general entities, both external
and internal, declared in the DTD. Duplicates are discarded.
For example in:

 <!DOCTYPE ex SYSTEM "ex.dtd" [
  <!ENTITY foo "foo">
  <!ENTITY bar "bar">
  <!ENTITY % baz "baz">
 ]>
 <ex/>

the interface provides access to foo and bar but not baz.
Every node in this map also implements the Entity interface.

The DOM Level 1 does not support editing entities, therefore
entities cannot be altered in any way.

B<Not In DOM Spec>: See XML::DOM::ignoreReadOnly to edit the DocumentType etc.

=item getNotations

A NamedNodeMap containing the notations declared in the DTD.
Duplicates are discarded. Every node in this map also
implements the Notation interface.

The DOM Level 1 does not support editing notations, therefore
notations cannot be altered in any way.

B<Not In DOM Spec>: See XML::DOM::ignoreReadOnly to edit the DocumentType etc.

=back

=head2 Additional methods not in the DOM Spec

=over 4

=item Creating and setting the DocumentType

A new DocumentType can be created with:

	$doctype = $doc->createDocumentType ($name, $sysId, $pubId, $internal);

To set (or replace) the DocumentType for a particular document, use:

	$doc->setDocType ($doctype);

=item getSysId and setSysId (sysId)

Returns or sets the system id.

=item getPubId and setPubId (pudId)

Returns or sets the public id.

=item setName (name)

Sets the name of the DTD, i.e. the name immediately following the
DOCTYPE keyword. Note that this should always be the same as the element
tag name of the root element.

=item getAttlistDecl (elemName)

Returns the AttlistDecl for the Element with the specified name, or undef.

=item getElementDecl (elemName)

Returns the ElementDecl for the Element with the specified name, or undef.

=item getEntity (entityName)

Returns the Entity with the specified name, or undef.

=item addAttlistDecl (elemName)

Adds a new AttDecl node with the specified elemName if one doesn't exist yet.
Returns the AttlistDecl (new or existing) node.

=item addElementDecl (elemName, model)

Adds a new ElementDecl node with the specified elemName and model if one doesn't 
exist yet.
Returns the AttlistDecl (new or existing) node. The model is ignored if one
already existed.

=item addEntity (notationName, value, sysId, pubId, ndata, parameter)

Adds a new Entity node. Don't use createEntity and appendChild, because it should
be added to the internal NamedNodeMap containing the entities.

Parameters:
 I<notationName> the entity name.
 I<value>        the entity value.
 I<sysId>        the system id (if any.)
 I<pubId>        the public id (if any.)
 I<ndata>        the NDATA declaration (if any, for general unparsed entities.)
 I<parameter>	 whether it is a parameter entity (%ent;) or not (&ent;).

SysId, pubId and ndata may be undefined.

DOMExceptions:

=over 4

=item * INVALID_CHARACTER_ERR

Raised if the notationName does not conform to the XML spec.

=back

=item addNotation (name, base, sysId, pubId)

Adds a new Notation object. 

Parameters:
 I<name>   the notation name.
 I<base>   the base to be used for resolving a relative URI.
 I<sysId>  the system id.
 I<pubId>  the public id.

Base, sysId, and pubId may all be undefined.
(These parameters are passed by the XML::Parser Notation handler.)

DOMExceptions:

=over 4

=item * INVALID_CHARACTER_ERR

Raised if the notationName does not conform to the XML spec.

=back

=item addAttDef (elemName, attrName, type, default, fixed)

Adds a new attribute definition. It will add the AttDef node to the AttlistDecl
if it exists. If an AttDef with the specified attrName already exists for the
given elemName, this function only generates a warning.

See XML::DOM::AttDef::new for the other parameters.

=item getDefaultAttrValue (elem, attr)

Returns the default attribute value as a string or undef, if none is available.

Parameters:
 I<elem>    The element tagName.
 I<attr>    The attribute name.

=item expandEntity (entity [, parameter])

Expands the specified entity or parameter entity (if parameter=1) and returns
its value as a string, or undef if the entity does not exist.
(The entity name should not contain the '%', '&' or ';' delimiters.)

=back