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Re: List of union

From: Michael Marchegay <mmarcheg@optonline.net>
Date: Thu, 3 Apr 2003 10:10:15 -0500
Message-ID: <002001c2f9f3$21acff30$8c01a8c0@mendossa>
To: "Henry S. Thompson" <ht@cogsci.ed.ac.uk>
Cc: <xmlschema-dev@w3.org>

"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·.

Michael

[2] http://www.w3.org/TR/xmlschema-2/#cos-list-of-atomic

>
> ht
>
> [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/
>  [mail really from me _always_ has this .sig -- mail without it is forged
spam]
>
Received on Thursday, 3 April 2003 10:10:25 GMT

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