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   Whoops too much (was Re: [xml-dev] Property dependency checking)

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From: "Bob Foster" <bob@xmlbuddy.com>

> Whoops. I got carried away and wrote:
> > ...If you're waiting for a significant
> > body of all-Schematron schemas, I would guess it will be a long wait.
> Talk about your flame-bait! If I had a cancel I would use it. My apologies
> to Rick and anyone else who got that far into the message. Of course there
> is a 'significant body' of all-Schematron schemas. The fact that I prefer to
> use Schematron to augment other kinds of schemas is beside the point.
Not beside the point at all.  We are not starting with a blank slate: Schematron 
arrives with grammar-based schema languages occupying centre stage, and 
encounters the widespread, tremendous, brave, pioneering and Pollyannaic hope that 
we can just extend grammars a little bit more we will reach some satisfactory point.  

That Schematron will be a layer on top of grammars for the forseeable future 
is just being realistic, not something to feel apologetic about.  

Every schema paradigm is can express conveniently a different range of
constraints.  That should be the starting point of thinking about schema
languages, rather than the DBMS vendor's el Sahaf-ism that one schema 
language is all that anyone needs, as was claimed in the early days of XML 

Just this week I had a support call from a user who said that their schema
was OK according to a highly-marketed tool, but failed in ours.  I checked and
it was a really trivial error (in that tool-- we use Xerces and MSXML 
which got that particular issue right, which may just be the luck of the draw.
The issue was to do with propagating namespace declarations from one schema
into an  <include>d schema, b.t.w.).  I am pretty  disturbed that such errors can be 
still present after all the time that WXS has been out; my advice from last 
year still seems to hold:-- contracts should specify that a couple of different 
tools be used to validate data when using WXS.

Rick Jelliffe


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