Date: Jan. 15, 2001
Link: http://www.thaiopensource.com/trex/tutorial.html
Source Author or Organization: James Clark

This is a tutorial for Tree Regular Expressions for XML (TREX), a new language for validating XML documents.

A TREX pattern specifies a pattern for the structure and content of an XML document, identifying a class of XML documents consisting of those documents that match the pattern. A TREX pattern is itself an XML document.

The tutorial assumes some familiarity with XML namespaces. There is a specification of the TREX language at http://www.thaiopensource.com/trex/spec.