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Re: LC-93 disjoint datatypes

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 11 Oct 2000 12:08:28 +0100
To: "C. M. Sperberg-McQueen" <cmsmcq@acm.org>
Cc: "Vun Kannon, David" <dvunkannon@kpmg.com>, W3C XML Schema Comments list <www-xml-schema-comments@w3.org>
Message-ID: <f5bn1gbvdn7.fsf@cogsci.ed.ac.uk>
"C. M. Sperberg-McQueen" <cmsmcq@acm.org> writes:

<snip/>

> The corresponding values in the other types are effectively
> shadowed and inaccessible.  (My earlier note said that xsi:type
> could be used to overcome this shadowing; I was wrong.  This
> was discussed speculatively in the WG, but is not in the spec.)

In fact you were right the first time.  The spec. specifically allows
xsi:type to identify a member of a union which was the declared type,
thereby allowing you to 'uncover' shadowed values.  See clause
2.2.1.4 of Type Derivation OK (Simple) [1].

I see that this inadvertently does not allow xsi:type to identify a
type _derived_ from a member type -- I'll fix that.

ht

[1]  http://www.w3.org/XML/Group/xmlschema-current/structures/structures.html#cos-st-derived-ok
-- 
  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 Wednesday, 11 October 2000 07:08:33 GMT

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