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

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Wed, 22 Mar 2006 09:49:45 -0500 (EST)
Message-Id: <20060322.094945.67088252.pfps@research.bell-labs.com>
To: phayes@ihmc.us
Cc: public-rdf-dawg-comments@w3.org, franconi@inf.unibz.it

From: Pat Hayes <phayes@ihmc.us>
Subject: Re: [OK] Re: [OK?] Re: comments on "SPARQL Query Language for RDF" (Non-respect for RDF Semantics)
Date: Wed, 8 Mar 2006 11:32:46 -0800

> >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

This sort of discussion needs to be in the document - along with more examples.

peer
Received on Wednesday, 22 March 2006 14:50:01 GMT

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