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Re: subgraph/entailment

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Thu, 08 Sep 2005 09:37:20 +0100
Message-ID: <431FF840.30802@hp.com>
To: Enrico Franconi <franconi@inf.unibz.it>
CC: jos.deroo@agfa.com, bparsia@isr.umd.edu, connolly@w3.org, public-rdf-dawg@w3.org, public-rdf-dawg-request@w3.org



Enrico Franconi wrote:
> 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.

For SPARQL to be useable, it must be possible to make queries against the 
exact triples in the base data.  Other modes shoudl also be possible 
determined by what service/graph/repository is being queried.

It must be possible to access the base data for SPARQL to be useable for any 
application that is involved in building a graph while at the same time 
accessing it.  I coined the term "zero-entailment" as I couldn't find extsing 
terminology.

I understand this to be part of the "Local Query" requirement. I had in mind 
that the query language be usable in applications that require access to the 
base data so they can add new triples, and they themselves deliver inference 
services to other applications.

We have already received comments where application require explicit access to 
the base data.  See the long thread starting from:
  http://lists.w3.org/Archives/Public/public-rdf-dawg-comments/2005Jun/0039
which includes explaination of the usage.

	Andy
Received on Thursday, 8 September 2005 08:38:01 GMT

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