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Re: Why datatypes?

• To: Murali Mani <mani@C...>
• Subject: Re: Why datatypes?
• From: Eddie Robertsson <erobertsson@a...>
• Date: Thu, 06 Jun 2002 10:14:48 +1000
• Cc: "Bullard, Claude L (Len)" <clbullar@i...>, "'Gustaf Liljegren'" <gustaf.liljegren@x...>, xml-dev@l...
• References: <Pine.SOL.4.33.0206051124590.5905-100000@p...>

Hi,

> but I think there recently have been efforts that schematron actually
> complements what is done by RELAX NG and XML-Schema -- that is very good.
>
> I have not followed schematron closely but I think what is really
> interesting contribution from schematron is the paradigm by which it does
> things -- the applications where it is useful, I am not sure.
>
> Again, if someone could provide some application scenarios and how
> schematron helps with some technical detail, I would be very glad.

I've been doing some work in this area for the simple reason that Schematron
complement both W3C XML Schema ("W3C") and RELAX-NG ("RNG") very well. Like
Len, I'm a huge fan of Schematron but I sometimes find that defining
structure in Schematron can be a bit complex and cumbersome. Since it's very
easy to define structure in both W3C and RNG it was natural to try to combine
them with Schematron to express the validation tasks that can not be
performed in W3C and RNG alone. For W3C you can use Schematron to overcome
the shortcomings for interleaving of elements or express co-occurrence
constraints. RNG does have some built-in support for co-occurrence
constraints but embedded Schematron rules can, for example, be used to
implement identity constraints that are not implemented in the current
version of RNG.
For both W3C and RNG there exist an XSLT stylesheet [1], [2] that will
extract the Schematron rules from the respective schema and merge these rules
into a complete Schematron schema that can be used for validation. I'm
currently writing up a paper on how to do this in both RNG and W3C which will
be finished shortly. In the meantime you can have a look at [3] for examples
and technical details. This paper only deals with embedded Schematron in W3C
but it works the same way for RNG.

Cheers,
/Eddie

[1] http://www.topologi.com/public/Schtrn_XSD/RNG2Schtrn.zip
[2] http://www.topologi.com/public/Schtrn_XSD/XSD2Schtrn.zip
[3] http://www.topologi.com/public/Schtrn_XSD/Paper.html


>
>
> thanks and regards - murali.
>
> On Wed, 5 Jun 2002, Bullard, Claude L (Len) wrote:
>
> > Someone usually does.  The SGMLers understand it and practiced it
> > virtually like a religion (the SGML Way).  It gets messy however to
> > ignore processing contexts if systems are to interoperate without
> > human interventions.  A reason for understanding what features XML
> > Schema, RELAX NG and/or Schematron enable is to pick the right tool to
> > get the right strength of agreement.  (Am I the only one who considers
> > Schematron almost heroic?  It is the one piece the others need
> > consistently and why I am holding out for DSDL.)
>
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