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Re: Selector Clarification

From: Rahul Srivastava <Rahul.Srivastava@Sun.COM>
Date: Wed, 10 Apr 2002 12:10:28 +0000 (Asia/Calcutta)
Message-Id: <200204100648.g3A6m0F09361@blr-root.India.Sun.COM>
To: xmlschema-dev@w3.org
Cc: jeni@jenitennison.com
> Jeni Tennison wrote...
> 
> Hi Rahul,
> 
> > But, is using a '.' as the XPath expr. for a selector valid?
> >
> > The rec. says:
> > http://www.w3.org/TR/xmlschema-1/#section-Identity-constraint-Definition-Validation-Rules
> > [[
> > Validation Rule: Identity-constraint Satisfied 
> >
> > For an element information item to be locally ·valid· with respect to an 
> > identity-constraint all of the following must be true:
> >
> > 1 The {selector}, with the element information item as the context node, evaluates to a 
> > node-set (as defined in [XPath]). [Definition:]  Call this the target node set. 
> >
> > 2 Each node in the ·target node set· is an element node among the descendants of the 
> > context node. 
> >
> > ....
> > ]]
> >
> > Looking at point 2 above, it reflects that, we cannot use '.' as the
> > XPath expr. for a selector. Does *descendants of the context node*
> > includes the context node?
> 
> Good point. I'd missed that. Usually, "descendants of the context
> node" doesn't include the context node, so I guess that would be the
> intention here.
> 
> > On the other hand the production rule for the XPath expr. for the
> > selector allows '.' as a valid XPath expr.
> > http://www.w3.org/TR/xmlschema-1/#coss-identity-constraint
> 
> Yes. This leaves us in a position where it's valid for a schema to
> contain a selector that has the xpath ., but it's not valid for an
> instance to contain an element that uses that identity constraint.
> 
> I'm not sure whether the intention of the WG was to allow identity
> constraints to select the context node or to disallow it. None of the
> implementations that I tested (XSV, MSXML, Xerces-C++, Xerces-J)
> complained about using <xs:selector xpath="." />, either within the
> schema or when there was an element in the instance document using the
> identity constraint.
> 
> You really need confirmation from W3C. Messages to
> www-xml-schema-comments@w3.org might elicit an official response.
> 

Thanks Jeni. I would ping XMLSchema WG.

Cheers,
Rahul.
Received on Wednesday, 10 April 2002 02:48:08 GMT

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