Version 1.4 of XSV released: derivation-by-restriction experiment

[ht@cogsci.ed.ac.uk (Henry S. Thompson)]

The web interface [1], the self-installer [2] and the sources [3] for
XSV, our W3C XML Schema validator, have all been updated with a new
version.

  "Version 1.4 introduces a cheap-but-effective approximation to
  enforcement of the constraints on derivation by restriction for
  complex type definitions.  This works by enforcing the subset
  invariant, and rejects any content model for a type definition
  derived by restriction which allows anything _not_ allowed by the
  base type definition's content model.  This is slightly weaker than
  the REC: i.e. everything it rules out is ruled out by the REC, but a
  few things ruled out by the REC will not be caught."

Note this is _not_ what the REC envisages, but it will go a lot
further towards enforcing interoperability between XSV and other
processors which _do_ enforce the REC as intended.

Nothing is as good as full conformance, but I hope this step, which
only took about three hours to implement, will be of use
never-the-less.

As with any substantial change, there may be bugs lurking -- I'll fix
them as quickly as possible provided bug reports contain enough
information to reproduce the bugs.

ht

[1] http://www.w3.org/2001/03/webdata/xsv
[2] ftp://ftp.cogsci.ed.ac.uk/pub/XSV/XSV14.EXE
[3] http://dev.w3.org/cvsweb/xmlschema/ -- see
    http://www.ltg.ed.ac.uk/~ht/xsv-status.html for installation instructions
-- 
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2001, part-time member of W3C Team
     2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
	    Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
		     URL: http://www.ltg.ed.ac.uk/~ht/