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

• To: "James Clark" <jjc@j...>
• Subject: Re: DTDs, W3C Schemas, RELAX NG, Schematron?
• From: Uche Ogbuji <uche.ogbuji@f...>
• Date: Mon, 24 Jun 2002 07:37:53 -0600
• Cc: "Don Box" <dbox@m...>, "John Cowan" <jcowan@r...>, xml-dev@l...
• In-reply-to: Message from "James Clark" <jjc@j...> of "Mon, 24 Jun 2002 12:15:19 +0700." <006201c21b3e$225c93d0$3500a8c0@b...>
• Sender: uche.ogbuji@f...

>  > I've found that the most important difference between RNG and XML
> > Schemas is wrt the underlying type model.
> >
> > Specifically, XML Schema uses named types to implicitly convey intention
> > as well as structure (a la Java, C++, C#). Anonymous types are 2nd class
> > citizens in XML Schema (they're type-equivalent with nothing).
> >
> > Relax NG has a much looser model (a la Perl) in which two things are
> > compatible if they share structure independent of a common, named type
> > definition.
> >
> > Each approach appeals to its own community of users in very deep ways.
> 
> I agree that the emphasis on named typing in W3C XML Schema is a profound
> difference from RNG.  One interesting question is whether it would be
> possible to build a schema language that supports named typing yet still has
> (at least most of) the simplicity and power of RNG.  However, I still have
> my doubts that named typing is appropriate for XML.  I would speculate that
> named typing is part of what makes use of DCOM and CORBA lead to the kind of
> relatively tight coupling that is exactly what I thought we were all trying
> to avoid by moving to XML.

I was going to respond to Don, but I decided to read on first, since I've already said more than enough on this topic in my discussion with Jonathan Robie.

I'm relieved to have to say no more than a hearty "amen".

I think that monolithic typing is one of the biggest dangers there is to all the unexpected value XML has brought software development.


-- 
Uche Ogbuji                                    Fourthought, Inc.
http://uche.ogbuji.net    http://4Suite.org    http://fourthought.com
Track chair, XML/Web Services One (San Jose, Boston): http://www.xmlconference.com/
DAML Reference - http://www.xml.com/pub/a/2002/05/01/damlref.html
The Languages of the Semantic Web - http://www.newarchitectmag.com/documents/s=2453/new1020218556549/index.html
XML, The Model Driven Architecture, and RDF @ XML Europe - http://www.xmleurope.com/2002/kttrack.asp#themodel

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  • Re: DTDs, W3C Schemas, RELAX NG, Schematron?
    • From: "James Clark" <jjc@j...>

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