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;


DocumentFragment is a "lightweight" or "minimal" 
Document object. It is very common to want to be able to 
extract a portion of a document's tree or to create a new fragment of a 
document. Imagine implementing a user command like cut or rearranging a 
document by moving fragments around. It is desirable to have an object 
which can hold such fragments and it is quite natural to use a Node for 
this purpose. While it is true that a Document object could 
fulfill this role, a Document object can potentially be a 
heavyweight object, depending on the underlying implementation. What is 
really needed for this is a very lightweight object. 
DocumentFragment is such an object.

Furthermore, various operations -- such as inserting nodes as children 
of another Node -- may take DocumentFragment 
objects as arguments; this results in all the child nodes of the 
DocumentFragment being moved to the child list of this node.

The children of a DocumentFragment node are zero or more 
nodes representing the tops of any sub-trees defining the structure of 
the document. DocumentFragment nodes do not need to be 
well-formed XML documents (although they do need to follow the rules 
imposed upon well-formed XML parsed entities, which can have multiple top 
nodes). For example, a DocumentFragment might have only one 
child and that child node could be a Text node. Such a 
structure model represents neither an HTML document nor a well-formed XML 
document.

When a DocumentFragment is inserted into a 
Document (or indeed any other Node that may 
take children) the children of the DocumentFragment and not 
the DocumentFragment itself are inserted into the 
Node. This makes the DocumentFragment very 
useful when the user wishes to create nodes that are siblings; the 
DocumentFragment acts as the parent of these nodes so that 
the user can use the standard methods from the Node 
interface, such as Node.insertBefore and 
Node.appendChild.

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

/**
 * <code>DocumentFragment</code> is a "lightweight" or "minimal" 
 * <code>Document</code> object. It is very common to want to be able to 
 * extract a portion of a document's tree or to create a new fragment of a 
 * document. Imagine implementing a user command like cut or rearranging a 
 * document by moving fragments around. It is desirable to have an object 
 * which can hold such fragments and it is quite natural to use a Node for 
 * this purpose. While it is true that a <code>Document</code> object could 
 * fulfill this role, a <code>Document</code> object can potentially be a 
 * heavyweight object, depending on the underlying implementation. What is 
 * really needed for this is a very lightweight object. 
 * <code>DocumentFragment</code> is such an object.
 * <p>Furthermore, various operations -- such as inserting nodes as children 
 * of another <code>Node</code> -- may take <code>DocumentFragment</code> 
 * objects as arguments; this results in all the child nodes of the 
 * <code>DocumentFragment</code> being moved to the child list of this node.
 * <p>The children of a <code>DocumentFragment</code> node are zero or more 
 * nodes representing the tops of any sub-trees defining the structure of 
 * the document. <code>DocumentFragment</code> nodes do not need to be 
 * well-formed XML documents (although they do need to follow the rules 
 * imposed upon well-formed XML parsed entities, which can have multiple top 
 * nodes). For example, a <code>DocumentFragment</code> might have only one 
 * child and that child node could be a <code>Text</code> node. Such a 
 * structure model represents neither an HTML document nor a well-formed XML 
 * document.
 * <p>When a <code>DocumentFragment</code> is inserted into a 
 * <code>Document</code> (or indeed any other <code>Node</code> that may 
 * take children) the children of the <code>DocumentFragment</code> and not 
 * the <code>DocumentFragment</code> itself are inserted into the 
 * <code>Node</code>. This makes the <code>DocumentFragment</code> very 
 * useful when the user wishes to create nodes that are siblings; the 
 * <code>DocumentFragment</code> acts as the parent of these nodes so that 
 * the user can use the standard methods from the <code>Node</code> 
 * interface, such as <code>Node.insertBefore</code> and 
 * <code>Node.appendChild</code>.
 * <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 DocumentFragment extends Node {
}