What is the DOM?
The Document Object Model (DOM) provides a standard programming model for working with XML. It is fully described in the W3C DOM specification.
The DOM was designed to:
- Provide a standard way to programmatically build, navigate or update and transform the contents of XML documents
- Establish a core set of vendor-and language-neutral application programming interfaces that could be used to meet the most common needs for developers working with and generating well-formed XML and HTML input and output streams
See Also
Concepts | How Do I?
Other Resources 
W3C Document Object Model (DOM) Level 1 Specification (Second Edition)