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Re: DTDs, W3C Schemas, RELAX NG, Schematron?

• To: <xml-dev@l...>
• Subject: Re: DTDs, W3C Schemas, RELAX NG, Schematron?
• From: "Rick Jelliffe" <ricko@a...>
• Date: Mon, 27 May 2002 18:53:26 +1000
• References: <2C61CCE8A870D211A523080009B94E430752B4AE@HQ5>

From: "Bullard, Claude L (Len)" <clbullar@i...>

> 2. Learn RELAX NG and XML Schemas.  Schematron has no official 
> standing, but without it, the weaknesses of RNG and XSD aren't 
> easy to overcome.  Databases typically need the ability to 
> specify co-occurrence constraints (if this value, then that 
> value).  So one needs it.

Schematron is currently being standardized as part of ISO DSDL. I hope
it will be an ISO standard by the end of this year, if everything goes smoothly.

I hope to fold in some of the ideas from the similar XCSL, whose author I met in
Barcelona last week, in particular the <let> element which allows variables 
to a certain extent: this will simplify dissecting strings into parts and treating 
their parts as numbers (e.g. dates, etc) with interrelationships.  At the moment 
this is possible but cumbersome.  

There are no backward-incompatible changes with Schematron 1.5 planned.
We are definitely targeting ISO Schematron as a convenient way to express
constraints that are difficult or confusing in other schema languages: express
simple relationships in other languages with simple content models, and leave
the complex constraints to Schematron schemas.

Cheers
Rick Jelliffe 

• References:
  • RE: DTDs, W3C Schemas, RELAX NG, Schematron?
    • From: "Bullard, Claude L (Len)" <clbullar@i...>

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