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   Re: Remember to RELAX (was RE: Are there still a lot of people usingDTD)

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  • From: "Simon St.Laurent" <simonstl@simonstl.com>
  • To: Bob Kline <bkline@rksystems.com>
  • Date: Tue, 01 Aug 2000 16:25:11 -0400

At 04:11 PM 8/1/00 -0400, Bob Kline wrote:
>I've assumed (from a distance) based on statements that use phrases like
>"upward compatibility" and "easy transition" that the functionality
>provided by RELAX was a subset of that provided by XML Schema.  However,
>I haven't found anything in the latter comparable to the attribute- 
>sensitive content models supported by RELAX.  Is this because XML Schema
>doesn't have such a feature, or just because it's harder to find things
>in the more densely-worded Schema documentation (or perhaps just because
>I'm not reading carefully enough)?

I think there may be a fundamental mismatch between the models used by the
two systems.  XML Schemas seems to take a top-down typing and inheritance
approach, whie RELAX uses a bottom-up approach with what feels to me like
set theory.  (They did announce the addition of a top-down model as well

You might be able to do attribute-sensitive content models using some of
the Schematron-like functionality that's found its way into recent drafts
of XML Schemas (look for tools using XPath), but I'm not sure it's possible
and hesitate to start digging.

For me, RELAX descriptions read more naturally, but it seems to be the
other way around for the object-oriented developers I always seem to end up
presenting to.

Simon St.Laurent
XML Elements of Style / XML: A Primer, 2nd Ed.
http://www.simonstl.com - XML essays and books


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