http://xml.apache.org/commons/components/external/: xml-commons provides an Apache-hosted set of DOM, SAX, and JAXP interfaces for use in other xml-based projects. Our hope is that we can standardize on both a common version and packaging scheme for these critical XML standards interfaces to make the lives of both our developers and users easier. The External Components portion of xml-commons contains interfaces that are defined by external standards organizations. For DOM, that's the W3C; for SAX it's David Megginson and sax.sourceforge.net; for JAXP it's Sun. 
/*
 * Copyright (c) 2004 World Wide Web Consortium,
 *
 * (Massachusetts Institute of Technology, European Research Consortium for
 * Informatics and Mathematics, Keio University). All Rights Reserved. This
 * work is distributed under the W3C(r) Software License [1] 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.
 *
 * [1] http://www.w3.org/Consortium/Legal/2002/copyright-software-20021231
 */

package org.w3c.dom;


Each Document has a doctype attribute whose value 
is either null or a DocumentType object. The 
DocumentType interface in the DOM 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 schema efforts 
on DTD representation are not clearly understood as of this writing.

DOM Level 3 doesn't support editing DocumentType nodes. 
DocumentType nodes are read-only.

See also the Document Object Model (DOM) Level 3 Core Specification.

/**
 * Each <code>Document</code> has a <code>doctype</code> attribute whose value 
 * is either <code>null</code> or a <code>DocumentType</code> object. The 
 * <code>DocumentType</code> interface in the DOM 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 schema efforts 
 * on DTD representation are not clearly understood as of this writing.
 * <p>DOM Level 3 doesn't support editing <code>DocumentType</code> nodes. 
 * <code>DocumentType</code> nodes are read-only.
 * <p>See also the <a href='http://www.w3.org/TR/2004/REC-DOM-Level-3-Core-20040407'>Document Object Model (DOM) Level 3 Core Specification</a>.
 */
public interface DocumentType extends Node {
    
The name of DTD; i.e., the name immediately following the 
DOCTYPE keyword.

/**
     * The name of DTD; i.e., the name immediately following the 
     * <code>DOCTYPE</code> keyword.
     */
    public String getName();

    
A NamedNodeMap containing the general entities, both 
external and internal, declared in the DTD. Parameter entities are 
not contained. Duplicates are discarded. For example in: 

<!DOCTYPE 
ex SYSTEM "ex.dtd" [ <!ENTITY foo "foo"> <!ENTITY bar 
"bar"> <!ENTITY bar "bar2"> <!ENTITY % baz "baz"> 
]> <ex/>

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

The DOM Level 2 does not support editing entities, therefore 
entities cannot be altered in any way.

/**
     * A <code>NamedNodeMap</code> containing the general entities, both 
     * external and internal, declared in the DTD. Parameter entities are 
     * not contained. Duplicates are discarded. For example in: 
     * <pre>&lt;!DOCTYPE 
     * ex SYSTEM "ex.dtd" [ &lt;!ENTITY foo "foo"&gt; &lt;!ENTITY bar 
     * "bar"&gt; &lt;!ENTITY bar "bar2"&gt; &lt;!ENTITY % baz "baz"&gt; 
     * ]&gt; &lt;ex/&gt;</pre>
     *  the interface provides access to <code>foo</code> 
     * and the first declaration of <code>bar</code> but not the second 
     * declaration of <code>bar</code> or <code>baz</code>. Every node in 
     * this map also implements the <code>Entity</code> interface.
     * <br>The DOM Level 2 does not support editing entities, therefore 
     * <code>entities</code> cannot be altered in any way.
     */
    public NamedNodeMap getEntities();

    
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 2 does not support editing notations, therefore 
notations cannot be altered in any way.

/**
     * A <code>NamedNodeMap</code> containing the notations declared in the 
     * DTD. Duplicates are discarded. Every node in this map also implements 
     * the <code>Notation</code> interface.
     * <br>The DOM Level 2 does not support editing notations, therefore 
     * <code>notations</code> cannot be altered in any way.
     */
    public NamedNodeMap getNotations();

    
The public identifier of the external subset.

Since:DOM Level 2
/**
     * The public identifier of the external subset.
     * @since DOM Level 2
     */
    public String getPublicId();

    
The system identifier of the external subset. This may be an absolute 
URI or not.

Since:DOM Level 2
/**
     * The system identifier of the external subset. This may be an absolute 
     * URI or not.
     * @since DOM Level 2
     */
    public String getSystemId();

    
The internal subset as a string, or null if there is none. 
This is does not contain the delimiting square brackets.

Note: The actual content returned depends on how much 
information is available to the implementation. This may vary 
depending on various parameters, including the XML processor used to 
build the document.

Since:DOM Level 2
/**
     * The internal subset as a string, or <code>null</code> if there is none. 
     * This is does not contain the delimiting square brackets.
     * <p ><b>Note:</b> The actual content returned depends on how much 
     * information is available to the implementation. This may vary 
     * depending on various parameters, including the XML processor used to 
     * build the document.
     * @since DOM Level 2
     */
    public String getInternalSubset();

}