I'm a co-author. Here's the abstract:
This document proposes a structural schema facility, Document Content
Description (DCD), for specifying rules covering the structure and content
of XML documents. The DCD proposal incorporates a subset of the XML-Data
Submission [XML-Data] and expresses it in a way which is consistent with
the ongoing W3C RDF (Resource Description Framework) [RDF] effort; in
particular, DCD is an RDF vocabulary. DCD is intended to define document
constraints in an XML syntax; these constraints may be used in the same
fashion as traditional XML DTDs. DCD also provides additional properties,
such as basic datatypes.
I have lots of opinions about it, which can wait for Montreal now. -Tim