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Re: [TF-ENT] A few comments on RDFS Entailment section

From: Axel Polleres <axel.polleres@deri.org>
Date: Tue, 6 Oct 2009 14:49:27 +0100
Cc: "Seaborne, Andy" <andy.seaborne@hp.com>, SPARQL WG <public-rdf-dawg@w3.org>
Message-Id: <333E5056-7E31-45D8-A7F6-AFB93BC13BBC@deri.org>
To: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
[snip]

>>> For now we have this as an open problem and how queries over  
>>> different
>>> named graphs should behave (do we take entailments into account that
>>> depend on triples from different named graphs). I'll try and add  
>>> notes
>>> for these two issues in the ent. regimes doc.
>
> I have added notes for this issue and for the named graphs issue that
> Steve mentioned to the doc, so we can't forget them. I hope I have
> some time during the flight/at the airport to think about how we can
> best handle this.
>
> Birte


FWIW, I think the issue of the behavior of names graphs (which I think
is essential to have at least a word about when) aiming to make  
entailment
usable in practice was already mentioned - in some disguise at [1].

Say, our dataset DS1 is:
   Default Graph: GraphFOAF, Graph1, Graph2, and any of the graphs  
that compose the default graph are also named graphs

where:

GraphFOAF is:
   foaf:Person rdfs:subClassOf foaf:Agent.

Graph1 is:
   :a a foaf:Person.

Graph2 is:
   :b a foaf:Person.

Query:

SELECT * {?x a foaf:Agent}

I assume that we agree that the answers should be

  ?x = :a ?x = :b

however, this one will always have an empty result:

SELECT * {GRAPH Graph1{ ?x a foaf:Agent}}

and I don't we how I could use the current BGP extension mechanism to  
change that
behavior except "merging" all ontologies I want to do reasoning aobut  
into *any*
named graph in the dataset.

At [1] it was proposed to parameterize the overall used ontologies  
with a
language construct, but that feature which would provide a workaround  
for the problem
didn't find much support and was dropped (It would BTW need an  
extension of the notion of Dataset, described in
[2]). That's ok, but woud there be any other ideas how to reasonably  
get ontological
inference into named graphs from a conceptual point of view?

best,
Axel

1. http://www.w3.org/2009/sparql/wiki/Feature:ParameterizedInference
2. Giovambattista Ianni, Thomas Krennwallner, Alessandra Martello, and  
Axel Polleres. Dynamic querying of mass-storage rdf data with rule- 
based entailment regimes. ISWC 2009.
Received on Tuesday, 6 October 2009 13:50:03 GMT

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