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   Re: [xml-dev] Re: How to redesign W3C XML Schema (Was: Remembering the o

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From: "Jochen Wiedmann" <joe@ispsoft.de>

> However, fact is, we *have* XML Schema. Vendors are backing
> it (for example, Sun :-) and I suppose they won't be interested
> in moving their tools to Schematron or Relax NG.  

XML-DEVers might be interested in these quotes from the draft OASIS
Content Assembly Mechanism spec, edited by David Webber who is
also active in the XML Schemas WG. http://www.oasis-open.org/committees/cam/
at s. 2.7.1

"...a transaction can be valid for the schema checks, but fail more extensive checks 
of the information integrity.  The result is that there is no way to provide consistent 
replicatable interchange specification using Schema or DTD. "

and at s 2.7.2

"Again one of the lessons learned is the "kitchen-sink" effect with schema used by itself 
in isolation. Such implementers strive to make a schema represent all possible combinations 
of an interchange, and rapidly the schema itself becomes voluminous and unwieldy, 
exactly the opposite of what they originally intended to create with a simple interchange definition." 

CAM seems to be proposing several mechanisms, some of which look like
Schematron (using Xpaths extended with declarative functions) or Examplotron. 
When we weight the acceptability of XML Schemas being universally aclaimed
as being large, we need to keep in mind that even though it is so big it still is not

As XML Schemas aligns its content models closer to the capabilities of RELAX NG,
the natural "subset" for people who don't need the complex type lattices would look
like RELAX NG anyway.

Rick Jelliffe


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