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Re: [Moderator Action] Inheritance and Identity-constraint

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 26 Feb 2001 17:20:39 +0000
To: Faroukh Fekravar <fekravar@austin.apc.slb.com>
Cc: Eddie Robertsson <eddie@allette.com.au>, xmlschema-dev@w3.org
Message-ID: <f5bpug5mkd4.fsf@cogsci.ed.ac.uk>
Faroukh Fekravar <fekravar@austin.apc.slb.com> writes:

> I don't understand why the second alternative (define the key within the Item
> element itself)
> is useless and moreover why it's not equal to the first one.

Because the location of the definition determines the scope of the
identity constraint.  Defining it on Item itself amounts to saying
"The value of the Id attribute of an Item is unique within that Item", 
which is trivially satisfied.

ht
-- 
  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 Monday, 26 February 2001 12:20:49 UTC

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