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Re: Expressing varying cardinalities of unordered elements in a complex-type

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 14 Feb 2002 10:39:23 +0000
To: "Mason Lee" <mgl@netspace.org>
Cc: "Eddie Robertsson" <eddie@allette.com.au>, <xmlschema-dev@w3.org>
Message-ID: <f5bbsesny90.fsf@cogsci.ed.ac.uk>
"Mason Lee" <mgl@netspace.org> writes:


> Out of curiousity, does anyone have any links to discussions as to
> why this sort of constraint wasn't included in the W3C XML Schema?
> Or more specifically, why "all" doesn't allow for cardinality >1?

This way it's essentially equivalent to attributes, but with element
syntax, i.e. one or none, any order.

The primary reason for not allowing arbitrary occurrence ranges is
implementatino complexity, but also because of lack of consensus as to
what it would _mean_ -- if you say 5 a's and 3 b's in any order, do
you mean:

aaaaabbb or bbbaaaaa


abaababa or bbaaaaab or ....?

Finally, there's a residual ideological point which says that if order
isn't significant, i.e. abba _means_ the same as aabb, then just fix
an order and simplify everyone's life.

  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 Thursday, 14 February 2002 05:39:40 UTC

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