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Re: [OK] Re: [OK?] Re: comments on "SPARQL Query Language for RDF" (Non-respect for RDF Semantics)

From: Pat Hayes <phayes@ihmc.us>
Date: Wed, 8 Mar 2006 11:32:46 -0800
Message-Id: <p06230902c034deb8ea03@[192.168.1.4]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: public-rdf-dawg-comments@w3.org, Enrico Franconi <franconi@inf.unibz.it>

>On 7 Mar 2006, at 00:26, Peter F. Patel-Schneider wrote:
>>>>(This also depends on just how the scoping graph is determined.)
>>>
>>>Mmhh, I'd say that it does not depend on that: the answer is uniquely
>>>determined up to bnode renaming. Why are you saying that?
>>
>>Well, changing the scoping graph can change the permissable answers, or at
>>least that is what I believe based on the SPARL documents.
>
>The scoping graph is always isomorphic to the original dataset - the 
>only things that may change are the names of the bnodes. This has no 
>effect on the answer set, apart from having possibly different bnode 
>names.

Quite. The bnode names used in the answer document are scoped 
separately from those in the query pattern, and need not (though may, 
a possibility we do not endorse but do allow) be the same as those 
used in the dataset, but they satisfy the same global patterns as the 
bnodes in the dataset graphs. The purpose of having the scoping graph 
at all is to ensure that the third condition is true; the reason for 
requiring it only to be isomorphic to - rather than identical to - 
the dataset, is to ensure the second condition; and the reason for 
requiring it to be bnode-disjoint with the query is to ensure the 
first condition. All of this has to do with bnode scoping, and none 
of it would be needed if there were no bnodes, in which case the 
definition could simply be that G (simply) entails B(Q).

Pat

>--e.
>
>Attachment converted: betelguese2:smime 32.p7s (    /    ) (0023D176)


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Received on Wednesday, 8 March 2006 19:33:03 GMT

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