I've updated my sample implementation of TREX in Java:

  http://www.thaiopensource.com/trex/jtrex.html

The main change is that it now supports datatyping using a real
implementation of XML Schema Part 2. This implementation supports
trex:role="datatype", so you can now +use xsd:list, xsd:union and
xsd:restriction to derive new datatypes within a TREX pattern. There are
a number of things not yet implemented (see
http://www.thaiopensource.com/trex/jdatatypes.html for details), some
because I just haven't got to them yet, some because I expect them to
change in the XML Schema Proposed Recommendation.

The datatyping implementation is independent of the rest of the
implementation, so it might be useful for other applications of XML
Schema Part 2.

For anybody whose uses Ant (the Java-based build tool), there's also a
TREX task that allows the TREX sample implementation to be used
conveniently from within Ant. See
http://www.thaiopensource.com/trex/trex-ant.html for more information.

James