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Re: Restricting Wildcards

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 27 Feb 2003 09:44:44 +0000
To: Noah Mendelsohn/Cambridge/IBM <noah_mendelsohn@us.ibm.com>
Cc: "Dare Obasanjo" <dareo@microsoft.com>, www-xml-schema-comments@w3.org, xmlschema-dev@w3.org
Message-ID: <f5bfzqam50z.fsf@erasmus.inf.ed.ac.uk>

Noah Mendelsohn/Cambridge/IBM <noah_mendelsohn@us.ibm.com> writes:

> Possibly dumb question:  does this cause any trouble regarding 
> restrictions form the anytype, which I believe has an any 
> processContents="skip".  If so, then our type hierarchy seems a bit shaky 
> at the moment.

Not dumb at all -- I was worried about that myself.

Yes, this does in fact rule out virtually all interesting complex type
definitions derived explicitly or implicitly from the ur-type.

Two possible fixes, which alas I think we should quickly put in to
1.1:

1) Modify clause 5 of Derivation Valid (Restriction, Complex) to
   have an explicit clause for the ur-type;
2) Modify the definition of *order-preserving* along the following
   lines:

  [Definition:] A complete functional mapping is order-preserving if
  each particle r in the domain R maps to a particle b in the range B
  which follows (not necessarily immediately) the particle in the
        ^^^^^^^
     does not precede
  range B mapped to by the predecessor of r, if any, where
  "predecessor" and "precede" are defined with respect to the order of
  the lists which constitute R and B.

Add:

   When more than one particle in the domain *R* (call the set of such
   particles *rr*) maps to the same particle *b* in the range *B*, then
   *all* of the following must be true:

   1 The sum of the {min occurs} of the particles in *rr* must be
     no less than the {min occurs} of *b*;

   2 *One* of the following must be true:

     2.1 The {max occurs} of *b* is _unbounded_.

     2.2 None of the {max occurs} of the particles in *rr* is
         _unbounded_, and their sum is no greater than the {max occurs}
         of *b*.

(2) has the advantage wrt (1) of allowing the schema-equivalent of
(a,a) to be derived from the schema-equivalent of a*, which is also
currently ruled out, but the disadvantage of being a tricky change
made in a hurry.  Since we don't know when 1.1 is coming, and this is
pretty important, I'd actually prefer to take a few days to look at
(2), and then add it to 2e.

ht
-- 
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
                      Half-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/
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Received on Thursday, 27 February 2003 04:44:48 GMT

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