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Re: unresolved MPEG-7 queries/issues

From: Henry S. Thompson <ht@cogsci.ed.ac.uk>
Date: 01 Mar 2001 19:50:22 +0000
To: Jane Hunter <jane@dstc.edu.au>
Cc: www-xml-schema-comments@w3.org
Message-ID: <f5br90hb75t.fsf@cogsci.ed.ac.uk>
Jane Hunter <jane@dstc.edu.au> writes:

> I'm resending four questions which I sent in an earlier email
> 
> (http://lists.w3.org/Archives/Public/www-xml-schema-comments/2001JanMar/
> 0000.html)
>  
> which remain unanswered. I'd appreciate your advice.

Sorry you haven't gotten official replies, probably my fault.

> -----------------------------
> 1. Global attributes
> 
> When referring to a global attribute whilst declaring a local 
> attribute,
> can you modify its "use" attribute value and expect this to overwrite 
> the
> original value?
> 
> Ex:
> 
> <attribute name="myAtt" type="integer"/>
> 
> <complexType>
>    <!-- can we expect the default value, 0, is specified
>         in the following local attribute? -->
>     <attribute ref="myAtt" use="default" value="0"/>
> </complexType>

Yes, you will be able to do this, we made a change.  There will be a
small change in the concrete syntax:

 <attribute name="myAtt" type="integer"/>
 
 <complexType>
    <!-- can we expect the default value, 0, is specified
         in the following local attribute? -->
     <attribute ref="myAtt" default="0"/>
 </complexType>

> 2. Root Elements
> 
> Is there a recommended way to specify a root element amongst global 
> elements in an instance document ?

There will be a change to make explicit that this can be a part of
initial schema assessment invocation.

> 3. Is it possible to derive an abstract complexType from a non-abstract
> complexType?

Yes.  It's slightly odd, but it's allowed.

> 4. Using derivation by restriction, can we change the content model
> of a group from choice[0,n] to sequence?

Yes, see [1], where it says "NOTE: This case allows the "unfolding" of
iterated disjunctions into sequences. It may be particularly useful
when the disjunction is an implicit one arising from the use of
substitution groups."

ht

[1] http://www.w3.org/TR/xmlschema-1/#rcase-MapAndSum
-- 
  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, 1 March 2001 14:50:26 GMT

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