xml-dev - Re: Schemata are not just constraints

[Rick Jelliffe <ricko@allette.com.au>]

Hi Martin, hope you are well. Happy New Year.

----- Original Message -----
From: Martin Bryan <mtbryan@sgml.u-net.com>
 > Agreed. The real problem is expressing constraints that apply across
> classes, rather than inheritable property constraints. (If class X > 12 do
> not require class Y, but do check that class Z is restricted to values A
or
> B.) This is one of the big "holes" in ebXML. We know its boundaries, but
are
> having difficulty filling it in.

Interestingly enough, Schematron may cover many of these kinds of things,
when processing a Post-Schema-Validation Infoset using a PSVI-aware version
of XPath.  One good reason for keeping class abstractions out of Schematron
is simply because, for people who want them, Schematron may get them for
free with the advent (presumably in 2002) of schema-aware XPath.

Cheers
Rick Jelliffe