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Re: can an attribute prohibited by restriction be added back through a subsequent extension?

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Thu, 22 Jan 2004 13:56:08 +0000
To: holstege@mathling.com
Cc: "Dare Obasanjo" <dareo@microsoft.com>, <xmlschema-dev@w3.org>, www-xml-schema-comments@w3.org
Message-ID: <f5b3ca89jev.fsf@erasmus.inf.ed.ac.uk>

The REC says in clause 1.5 of Schema Component Constraint: Derivation
Valid (Extension) [1]:

 Note: This requirement ensures that nothing removed by a restriction
 is subsequently added back by an extension.

That (rather than clause 1.2 as I think Mary was suggesting) is where
the REC tries to answer "no" to the question of "whether an attribute
[or element] removed by restriction could be added back in an
extension."  However the constraint itself, in my view, fails to
achieve this, so processors which allow it are not broken.

I think we should fix this one way or another -- what do you think is

  1) No constraint on re-introduction;
  2) No re-introduction of any kind (apparent intention of current REC);
  3) Re-introduction of unchanged originals only (what the current REC
     actually says)?


[1] http://www.w3.org/TR/xmlschema-1/#cos-ct-extends
 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@inf.ed.ac.uk
                   URL: http://www.ltg.ed.ac.uk/~ht/
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Received on Thursday, 22 January 2004 09:00:54 UTC

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