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Re: List of union

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 03 Apr 2003 16:38:50 +0100
To: "Michael Marchegay" <mmarcheg@optonline.net>
Cc: <xmlschema-dev@w3.org>
Message-ID: <f5bvfxvwpyt.fsf@erasmus.inf.ed.ac.uk>

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

> "Henry S. Thompson" <ht@cogsci.ed.ac.uk> writes:
> 
> > "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)."
> 
> Thanks for the pointer.
> 
> However, I am wondering if there isn't a partial redundancy - that can
> confound the reader - between "Schema Component Constraint: Derivation Valid
> (Restriction, Simple)" and "Schema Component Constraint: list of atomic":
> 
> Schema Component Constraint: list of atomic [2]
>     If {variety} is ·list·, then the {variety} of {item type definition}
> ·must· be ·atomic· or ·union·.

Redundant yes, but not wrong.

ht
-- 
  Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
                      Half-time member of W3C Team
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	    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 10:38:56 GMT

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