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On told-bnodes in queries

From: Enrico Franconi <franconi@inf.unibz.it>
Date: Wed, 2 Nov 2005 14:41:01 +0100
Message-Id: <DFB788F5-C274-423E-8E24-4AABA422ABBA@inf.unibz.it>
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
To: Pat Hayes <phayes@ihmc.us>

Hi Pat,
Here it is the example of why the definition of query answer using  
union rather RDF-merge does not work as desired to capture what I  
called (l3):

> l3) the bnodes names in a query have to be treated as told-bnodes,  
> i.e., they have to match only with bnodes with the same name in the  
> dataset.

GRAPH: :s :p _:b .

query 1:  { ?x :p _:a }
query 2:  { ?x :p _:b }

According to (l3) query 1 has the empty answer,
while query 2 has the answer [?x/:s].

using the semantics proposed by you:

G |= (G U Q)[s]

both queries have the answer [?x/:s]

In this case the user may wrongly gather that the triple <:s :p _:a>  
was *explicitely* asserted in the graph.

cheers
--e.
Received on Wednesday, 2 November 2005 13:41:19 GMT

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