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Re: simpleType redefinition - must it be a restriction?

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 08 Jan 2002 08:48:49 +0000
To: Mark Feblowitz <mfeblowitz@frictionless.com>
Cc: "'Jeni Tennison'" <jeni@jenitennison.com>, "Xmlschema-Dev (E-mail)" <xmlschema-dev@w3.org>
Message-ID: <f5bsn9hjki6.fsf@cogsci.ed.ac.uk>
Mark Feblowitz <mfeblowitz@frictionless.com> writes:

> [can we have our cake and eat it too, wrt enumerated type
>  definitions]

I think your summary of the situation is accurate and comprehensive.

I'd only add that labelling the approach of using a union of an
explicit enumeration and a string as 'only ... documentation' is
perhaps overly dismissive.  The force of the documentation can be
quite significant and useful, i.e. an indication that members of the
explicit enumeration will receive appropriate processing, while others
will be ignored.  Note further that the type information in the PSVI
signals to the application which branch of the union was taken.

The bottom line is that we've tried in the XML Schema design to
guarantee certain invariants to application designers, and allowing
schema users to extend the membership of enumerated types would not
allow _any_ invariant.

Sorry this doesn't meet your needs, but I guess what I'm trying to say
is you might like to consider what the burden on applications would be
if you _could_ write the schema you want to.

  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
          W3C Fellow 1999--2001, part-time member of W3C Team
     2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
	    Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
		     URL: http://www.ltg.ed.ac.uk/~ht/
Received on Tuesday, 8 January 2002 03:48:54 UTC

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