Date: Jan. 15, 2001
Link: http://catcode.com/relax_tut/index.html
Source Author or Organization: J. David Eisenberg

REgular LAnguage description for XML (RELAX) is an alternative approach to the Document Type Definition (DTD) for providing a reference document for XML documents.

This tutorial explains XML document validation in general, then covers some of the language's capabilities to make a case for RELAX as a better reference document method. A RELAX document gives all the information that a DTD does and is more readable. It also enables you to specify if an element must enclose numeric data within a certain range or belong to one of a specific list of values.