I understand what you mean with the assertions.  And schematron-like
assertions in the schema itself is helpful.  Perhaps that is the best
solution.  But I've found schematron is a bit too technical for business
folks.  They can create models using xml schema with a good wysiwyg tool,
but the assertions are over their head.
Perhaps folks are looking for something that is impossible, a simple way to
manage large logical models and smaller physical ones (staying in sync).  I
can always hope for the impossible, right?



-----Original Message-----
From: Michael Kay [mailto:mike@s...] 
Sent: Friday, July 17, 2009 1:21 PM
To: 'Paul Kiel'; 'Costello, Roger L.'; xmlschema-dev@w...
Subject: RE: [XML Schema 1.1] No changes to derive-by-restriction, right?
(just a simplification of its description in the specification)

> 
> Of course maybe I have this all wrong.  Perhaps the lack of 
> rules will give some freedom and lead to some interesting 
> implementations of this underused feature.  I would love to 
> see that happen.

Personally I suspect that with XSD 1.1, most restricted types will be
specified not by providing a restricted grammar, but by using the original
grammar in conjunction with assertions. For example, if you want to disallow
an optional element from the content model, it's much easier to assert that
the element is absent than to define a restricted grammar in which it is
omitted.

Regards,

Michael Kay
http://www.saxonica.com/
http://twitter.com/michaelhkay