RelaxNG is a SchemaLanguageForXML based on RegularTreeGrammars^?. It is (suprisingly) more powerful and easier to use and learn than XMLSchema. The RelaxNG standard inclused a well-defined formal semantics.

There is also a (currently not standardized) concrete syntax in addition to the standard XML syntax.

Jing is the RelaxNG validator of JamesClark^?: http://www.thaiopensource.com/relaxng/jing.html

-- MartinBravenboer - 30 May 2002