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RE: Impact of the usage of unique identifier as URN into XML docu ment s ?

From: Hess Yvan <yvan.hess@imtf.ch>
Date: Mon, 15 Mar 2004 17:26:45 +0100
Message-ID: <DF7EC83D7AFBD411965B0008C7596EC5E0D4B2@imtfexchange.imtf.ch>
To: "'ht@inf.ed.ac.uk'" <ht@inf.ed.ac.uk>
Cc: "'xmlschema-dev@w3.org'" <xmlschema-dev@w3.org>

document is the root element of my XML document and it is for this reason I
choose "." as XPath expression of my key and I included it in my element
declaration as illustrated bellow: 

   <xs:element name="document">
      <xs:complexType>
         <xs:sequence>
            <xs:element name="metadata" type="MetadataType"/>
         </xs:sequence>
         <xs:attribute name="version" type="xs:string" use="required"/>
         <xs:attribute name="id" type="xs:string" use="required"/>
      </xs:complexType>
      <xs:key name="DocIdentifier">
         <xs:selector xpath="."/>
         <xs:field xpath="@id"/>
      </xs:key>
   </xs:element>


Choosing <xs:selector xpath=".//my:document"/> as you recommended will not
work or I am wrong, am I? What is the solution in this context?

Regards. Yvan


-----Original Message-----
From: ht@inf.ed.ac.uk [mailto:ht@inf.ed.ac.uk]
Sent: lundi, 15. mars 2004 16:18
To: Hess Yvan
Cc: 'xmlschema-dev@w3.org'
Subject: Re: Impact of the usage of unique identifier as URN into XML
document s ?


Hess Yvan <yvan.hess@imtf.ch> writes:

> <xs:key name="DocIdentifier">
>   <xs:selector xpath="."/> 
>   <xs:field xpath="@id"/>
> </xs:key>

This does not have the desired effect, it will always be true, as
there is only ever one id attribute on a 'document' element.  To have
this do useful work, you need to change it to

<xs:key name="DocIdentifier">
   <xs:selector xpath=".//my:document"/> 
   <xs:field xpath="@id"/>
</xs:key>

and move it to within an element declaration for an element which
scopes all your 'document' nodes.

> It works fine, but I don't know the future impacts/limitation of such
> choice, specially concerning the usage of URN as unique identifier in
> conjunction with others XML technologies. Does anybody have any comments,
> suggestions or best practices about this subject? Can you see future
> limitation?

I don't foresee any future problems with this -- the actual _type_ of
the attribute you call 'id' is completely within your control.

ht
-- 
 Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
                     Half-time member of W3C Team
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Received on Monday, 15 March 2004 11:32:52 UTC

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