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Re: Fwd: Re: Comments about the semantics of property paths

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Wed, 26 Jan 2011 14:39:05 +0000
Message-ID: <4D403209.1090901@epimorphics.com>
To: Matthew Perry <matthew.perry@oracle.com>
CC: SPARQL Working Group <public-rdf-dawg@w3.org>


On 26/01/11 13:53, Matthew Perry wrote:
> I think this should work for the sum age query.
>
> SELECT SUM(?A)
> WHERE
> { ?F :age ?A
> { SELECT DISTINCT ?F
> WHERE
> { :me (:friend)+ ?F } }}
>
> It seems that, in general, DISTINCT will work as a there exists query
> when URIs and blank nodes are the endpoint of a path because we have a
> one-to-one mapping between URI/BN values and graph vertices, but we get
> a one-to-many mapping from literal values to vertices.

Yes, that example addresses Jorge's use case and contrasts nicely with 
the basket example where there is a need for duplicate matches from the 
property path itself (although, in the syntax triple patterns are 
property paths of length 1).

	Andy
Received on Wednesday, 26 January 2011 14:40:07 GMT

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