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Re: List of union

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 03 Apr 2003 09:37:16 +0100
To: "Michael Marchegay" <mmarcheg@optonline.net>
Cc: <xmlschema-dev@w3.org>
Message-ID: <f5bhe9g2czn.fsf@erasmus.inf.ed.ac.uk>

"Michael Marchegay" <mmarcheg@optonline.net> writes:

> My understanding of the concept of list, as defined in XML Schema
> recommendation, would make me think that a list whose {item type definition}
> has the variety union is valid only if the union does not contain any simple
> type definitions having the variety list among its {member type
> definitions}.
> I looked in the XML Schema Part 1 and 2 for some text confirming that, but I
> haven't found it.  I also looked in the archives of xmlschema-dev list for
> an explanation, and I have found confirmation of my hypothesis, but none of
> the answers refere to a clause stating it clearly.  Is this restriction
> explained somewhere in the recommendation?

In Schema Component Constraint: Derivation Valid (Restriction, Simple) [1]

   "2 If the {variety} is list, then  all of the following must be true:
      2.1 The {item type definition} must have a {variety} of atomic
      or union (in which case all the {member type definitions} must
      be atomic)."


[1] http://www.w3.org/TR/xmlschema-1/#cos-st-restricts
  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, 3 April 2003 03:37:18 UTC

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