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Re: Equivalence classes

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 19 Feb 2000 10:03:02 +0000
To: www-xml-schema-comments@w3.org
Message-ID: <f5bya8hik6h.fsf@cogsci.ed.ac.uk>
Philip Wadler <wadler@research.bell-labs.com> writes:

> Henry writes:
> > As currently spec'ed you can only nominate a global element as the
> > exemplar of an equivalence class, so you example is invalid to start
> > with.
> Thanks, that answers my first question (as I suspected, in the negative).
> But not my second, repeated here.
> > If it's not possible, what was the rationale for omitting it?
> By the way, I consider this on the critical path to getting a report
> out the door, in the sense that the report needs to explain rationales
> for this and other decisions.  Cheers, -- P

W3C specs do _not_ contain rationales for their design decisions:
that would make them monsters beyond reading.

The rationale in this case is that there is no guarantee of uniqueness 
of reference: there can be multiple local element declarations with the same 
name within different complex types, and thus no way with a 'ref'
attribute of type QName to distinguish between them.  XPath could do
it, but the additional complexity was not judged worth the marginal
increase in functionality.

  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 Saturday, 19 February 2000 05:03:05 UTC

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