The World Wide Web Consortium standards for representation of documents (for instance, Html Documents with Cascading Style Sheets and Extensible Markup Language documents) as an object model. Three levels of the specification exist, where each is a superset of the last, and levels 2 and 3 are separated into modules. See www.w3.org 
for details. Level 1 and most of level 2 are supported by major web browsers for Javascript (the primary audience).
Often mistakenly thought to be part of Java Script, as that language is most commonly used to manipulate the Document Object Model and its predecessors. --Nick Fitzsimons
The group news:comp.lang.javascript is always ready to cheerfully and helpfully field questions about HTML and DOM.
The Document Object Model is also used to represent the parse trees for XML (Extensible Markup Language) documents. -- Edward Kiser
Category Xml {Edit Hint: why this category, may I ask} It links a collection of pages related in some way or another to XML.
See original on c2.com