The purpose of the OASIS RELAX NG TC is to create a specification for a schema language for XML based on the TREX proposal (http://www.thaiopensource.com/trex/).
While this article doesn't contain an exhaustive review of all the features of RELAX NG, it will give you a good idea of how to use the main parts of the compact syntax.
Trang converts between different schema languages for XML. It supports the following languages: * RELAX NG (XML syntax) * RELAX NG compact syntax * XML 1.0 DTDs * W3C XML Schema