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Re: issue#rdfSemantics : use cases

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Wed, 14 Sep 2005 12:02:20 +0100
Message-ID: <4328033C.8010000@hp.com>
To: Steve Harris <S.W.Harris@ecs.soton.ac.uk>
CC: RDF Data Access Working Group <public-rdf-dawg@w3.org>

Steve Harris wrote:
> On Wed, Sep 14, 2005 at 10:54:51 +0100, Andy Seaborne wrote:
>>== Data 1:
>>:x <p> "z"  .
>>_:a <p> "z" .
>>== Query:
>>SELECT * { ?s <p> ?o }
>>== Results
>>s/:x  p/<p>  o/"z"
>>s/_:a p/<p>  o/"z"
>>And the application wishes to add:
>>_:a <q> "y" .
>>that is, a tripe with the bNode in the abstract syntax form of the grap as 
>>This requires both solutions to be returned in the example query.
> I feel like being pedantic today, so I'l note that the query engine could
> also, perfectly legally return
> s/_:zzz  p/<p>  o/"z"
> to that query, as bNodes aren't round tripped in SPARQL, c.f. last
> paragraph of "Templates with Blank Nodes":
> "The use of variable ?x in the template, which in this example will be
>  bound to blank nodes (which have labels _:a and _:b in the data) causes
>  different blank node labels (_:v1 and _:v2) as shown by the results."

It's not a template - it's a SELECT query but the general point is true.


The point is it should not be wrong to return the bNode so that the 
application can (local usage) access the graph abstract syntax directly.


> so at the very least this usecase requires knowledge of how bnodes are
> handled in results in the implementation.
> - Steve
Received on Wednesday, 14 September 2005 11:04:53 UTC

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