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Re: UPA Question

From: George Cristian Bina <george@oxygenxml.com>
Date: Tue, 28 Nov 2006 18:54:29 +0200
Message-ID: <456C69C5.7010407@oxygenxml.com>
To: Michael Kay <mike@saxonica.com>
Cc: 'Erik Johnson' <ejohnson@epicor.com>, xmlschema-dev@w3.org

Hi Mike,

What do you think about the following fragment? To me it seems that it 
states clearly that referring to a group from two locations results in 
different particles.

http://www.w3.org/TR/xmlschema-1/#cos-nonambig
***
Since this constraint is expressed at the component level, it applies to 
content models whose origins (e.g. via type derivation and references to 
named model groups) are no longer evident. So particles at different 
points in the content model are always distinct from one another, even 
if they originated from the same named model group.
***

Best Regards,
George
---------------------------------------------------------------------
George Cristian Bina
<oXygen/> XML Editor, Schema Editor and XSLT Editor/Debugger
http://www.oxygenxml.com


Michael Kay wrote:
> UPA is violated if the particle with which to validate ElementA1 cannot 
> be uniquely determined. So I think it boils down to a question of 
> whether the ElementA1 particle reached via grpA is the same particle as 
> the ElementA1 particle reached via grpB and grpA. In Saxon it is, and 
> therefore no UPA violation is reported. The fact that the same particle 
> can be selected in two different ways is not an ambiguity, because it is 
> the same particle.
>  
> The content model clearly would be ambiguous if you expanded the named 
> groups by copying them. But I don't think the spec says you should do 
> that; in fact it says that named groups are incorporated into a term "by 
> reference". So I would defend Saxon's result.
>  
> However, the spec itself admits that the "notion of component identity 
> ... is only incompletely defined by this version of this specification." 
> So it's muddy water.
>  
>  
> Michael Kay
> http://www.saxonica.com/
> 
>     ------------------------------------------------------------------------
>     *From:* xmlschema-dev-request@w3.org
>     [mailto:xmlschema-dev-request@w3.org] *On Behalf Of *Erik Johnson
>     *Sent:* 28 November 2006 01:18
>     *To:* xmlschema-dev@w3.org
>     *Subject:* UPA Question
> 
>     I have two toolkits (from the same company, BTW) that compile the
>     schema shown below differently.  One says the schema is fine while
>     the other says the choice inside grpC/ElementC1 violates the UPA
>     rule.  This example looks a bit contrived, but itís a reduction from
>     something a lot more complex that obviously could be re-factored.  
>     On the surface, I can see why one might think having grpA in choice
>     particles at two levels within ElementC1 makes the content
>     ambiguous.  But after thinking about it, I donít think that the
>     content model is ambiguous.  My question is which toolkit is right
>     and which one gets my bug report?  Thanks!
> 
>      
> 
>     <xs:schema id="XMLSchema1"
> 
>                       targetNamespace="uri:erik:upaQuestion"
> 
>                       elementFormDefault="qualified"
> 
>                       xmlns="uri:erik:upaQuestion"
> 
>                       xmlns:tns="uri:erik:upaQuestion"
> 
>                       xmlns:xs="http://www.w3.org/2001/XMLSchema">
> 
>      
> 
>           <xs:group name="grpA">
> 
>                 <xs:sequence>
> 
>                       <xs:element name="ElementA1"/>
> 
>                 </xs:sequence>
> 
>           </xs:group>
> 
>      
> 
>           <xs:group name="grpB">
> 
>                 <xs:choice>
> 
>                       <xs:element name="ElementB1" />
> 
>                       <xs:group ref="tns:grpA"/>
> 
>                 </xs:choice>
> 
>           </xs:group>
> 
>      
> 
>           <xs:group name="grpC">
> 
>                 <xs:sequence>
> 
>                       <xs:element name="ElementC1">
> 
>                             <xs:complexType>
> 
>                                   <xs:sequence>
> 
>                                         <xs:choice>
> 
>                                               <xs:group ref="tns:grpB"/>
> 
>                                               <xs:group ref="tns:grpA"/>
> 
>                                         </xs:choice>
> 
>                                   </xs:sequence>
> 
>                             </xs:complexType>
> 
>                       </xs:element>
> 
>                 </xs:sequence>
> 
>           </xs:group>
> 
>      
> 
>           <xs:element name="RootElement">
> 
>                 <xs:complexType>
> 
>                       <xs:choice>
> 
>                             <xs:group ref="tns:grpC"/>
> 
>                             <xs:sequence>
> 
>                                   <xs:element name="OtherStuff" />
> 
>                             </xs:sequence>
> 
>                       </xs:choice>
> 
>                 </xs:complexType>
> 
>           </xs:element>
> 
>      
> 
>     </xs:schema>
> 
>      
> 
>      
> 
Received on Tuesday, 28 November 2006 16:55:03 UTC

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