In the announcement, Clark indicates that the main change
to the implementation is that it now supports datatyping
using a "real implementation" of the W3C's XML Schema Part 2:
Datatypes Candidate Recommendation. (Note that the TREX
language itself does not have any system of datatypes built
in, but is instead designed to "partner" with a datatyping
vocabulary such as the W3C's XML Schema Part 2: Datatypes.)
The implementation does not support every datatype in the W3C
Candidate Recommendation; Clark provides a document
that details which datatypes are supported and which are
not.
The hallmarks of TREX, which Clark introduced publicly
only one month ago, are its simplicity and flexibility. It
attempts only to specify patterns for defining the tree
structure and content of specific classes of XML documents,
without aiming to assist in interpretation or processing of
the documents. The TREX site includes both a tutorial
that provides extensive examples of the language, and a
formal specification
that details its syntax and semantics.
TREX figured prominently in a recent xml-dev
discussion thread (which Schematron
creator Rick Jelliffe started with the subject line "Are we losing out because of grammars?") discussing the
merits of, and differences between, various XML schema
languages (including Murata's RELAX, Jelliffe's
Schematron, and the W3C's XML Schema language in addition to
TREX). Key parts of the discussion are very nicely summarized and
elucidated by Leigh Dodds in his February 7th XML-Deviant
column.
Clark also contributed another recent message to xml-dev
in which he
provides details about "areas where TREX allows things
that are difficult or impossible with the W3C's schema
language".
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