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Re: subgraph/entailment

From: Enrico Franconi <franconi@inf.unibz.it>
Date: Thu, 8 Sep 2005 10:18:21 +0200
Message-Id: <6FF0B3D6-1B18-4579-93EF-0650A0E396C0@inf.unibz.it>
Cc: bparsia@isr.umd.edu, connolly@w3.org, public-rdf-dawg@w3.org, public-rdf-dawg-request@w3.org
To: jos.deroo@agfa.com

On 8 Sep 2005, at 10:03, jos.deroo@agfa.com wrote:
>>>>> I should *not* get the bnode coming from the redundant
>>>>> triple, but simply {<http://example.org/book/book1>}.
>>>>
>>>> Otoh, for
>>>>
>>>> CONSTRUCT { ?x dc:title "SPARQL" }
>>>> WHERE { ?x dc:title "SPARQL" }
>>>>
>>>> I actually get
>>>>
>>>> <http://example.org/book/book1> dc:title "SPARQL".
>>>> _:b_0_ dc:title "SPARQL".
>>>>
>>>> which I assume to be fine, no?
>>>>
>>>
>>> The result form shouldn't affect the (number of) results
>>> unless there's something expicit in the form which does that
>>> (which I don't think is true for construct). At least,
>>> that's what I would expect!
>>>
>>
>> Indeed. I expect no bnode in this case too, independently on
>> the type of query, since the answer should be the same as the
>> one with the dataset without the bnode.
>>
>
> [[
> The CONSTRUCT result form returns a single RDF graph
> specified by a graph template. The result is an RDF
> graph formed by taking each query solution in the
> solution sequence, substituting for the variables
> into the graph template and combining the triples
> into a single RDF graph by set union.
> ]]
> http://www.w3.org/2001/sw/DataAccess/rq23/#construct
>
> and
>
> ###
> <http://example.org/book/book1> dc:title "SPARQL".
> _:b_0_ dc:title "SPARQL".
> ###
>
> is a single RDF graph and a single result and I don't
> see any issue wrt to bnodes or minimality in it;
> what is the issue in this case?

As I argued with my latest long email <http://www.w3.org/mid/ 
E1ED5pH-0005ls-Kz@lisa.w3.org>, there only one binding (query  
solution) for ?x according to RDF-MT semantics, namely <http:// 
example.org/book/book1>.
Therefore, substituting the variable ?x in the graph template gives  
you only the triple

<http://example.org/book/book1> dc:title "SPARQL".

even in the case of the dataset

<http://example.org/book/book1> dc:title "SPARQL" .
_:b dc:title "SPARQL" .


Is there something I'm missing?
--e.
Received on Thursday, 8 September 2005 08:18:37 GMT

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