TREX - a new schema language

[James Clark <jjc@jclark.com>]

I've designed and implemented a small, simple schema language.  It's
called TREX (Tree Regular Expressions for XML).  Calling it a schema
language is perhaps misleading: it's goal is purely validation. It
doesn't aim to assist in interpreting or processing the document.  The
post-validation infoset is exactly the same as the pre-validation
infoset.

You can find more, including a tutorial, a (relatively) formal spec and
a sample implementation in Java on top of SAX2 at:

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

It's basically the type system of XDuce with an XML syntax and with a
bunch of additional features (like support for attributes and
namespaces) needed to make it a practical language for structure
validation. Of existing Schema languages, it's closest to RELAX. It's
not tied to any particular datatyping language; rather, the idea is that
you can plug whatever datatyping language you want (eg XML Schemas Part
2).

This is the first release, so there will certainly be bugs in both the
documents and the implementation.

I plan to continue to refine both the design and the implementation.
Input is welcome.

James