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RE: incorrect unique constraint in Primer?

From: Priscilla Walmsley <priscilla@walmsley.com>
Date: Mon, 20 Oct 2003 17:59:59 -0400
To: "'Jan Hidders'" <jan.hidders@ua.ac.be>, <www-xml-schema-comments@w3.org>
Message-ID: <005d01c39755$820dc260$ef2efea9@WALMSLEYPH>

Hello Jan,

You are absolutely correct.  This has been addressed by an erratum [1],
and will be corrected in the second edition of the Primer.

Thanks for your comments,
Priscilla

[1] http://www.w3.org/2001/05/xmlschema-errata#e0-26


> -----Original Message-----
> From: www-xml-schema-comments-request@w3.org 
> [mailto:www-xml-schema-comments-request@w3.org] On Behalf Of 
> Jan Hidders
> Sent: Monday, October 20, 2003 12:23 PM
> To: www-xml-schema-comments@w3.org
> Subject: incorrect unique constraint in Primer?
> 
> 
> 
> I have a question about the example of a unique constraint in 
> the primer 
> in section 5.1.  The following example is given:
> 
>   <unique name="dummy1">
>    <selector xpath="r:regions/r:zip"/>
>    <field    xpath="@code"/>
>    <field    xpath="r:part/@number"/>
>   </unique>
> 
> However, since a zip element may contain more than 1 parts the path 
> expression "r:part/@number" does not result always in a single node, 
> which makes this an illegal unique constraint (cfr. section 3.11.1 in 
> XML Schema Part 1: Structures).
> 
> Actually I very strongly suspect that the constraint that they are 
> trying to express is actually not expressible as a unique constraint.
> 
> Is this correct or have I misunderstood something?
> 
> -- 
>     Jan Hidders
> 
>   
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> 
Received on Monday, 20 October 2003 18:00:16 UTC

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