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Re: [TF-ENT] Querying datasets with default plus named graphs

From: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
Date: Thu, 8 Oct 2009 11:34:36 +0100
Message-ID: <492f2b0b0910080334n38fb2a63r3dff36d95e2e88dd@mail.gmail.com>
To: Ivan Herman <ivan@w3.org>
Cc: Axel Polleres <axel.polleres@deri.org>, "Seaborne, Andy" <andy.seaborne@hp.com>, SPARQL Working Group <public-rdf-dawg@w3.org>
2009/10/8 Ivan Herman <ivan@w3.org>:
>
> Axel Polleres wrote:
[snip]
>> +1 to keep entailments local to the separate  graphs in the DS
>> (<chairhatoff> although  I  personally consider it a drawback that you
>> can't refer to ontologies from named graphs)
>
> Hm. Yes, this seems to be a consequence which is a bit disagreeable
> indeed:-(
>
> In OWL, I can of course use owl:import in my WHERE clause (Birte, this is
> all right, isn't it?) which is not that bad, the user has to make things
> explicit. But this does not help the RDFS case.

In OWL you can use imports, but I suppose you mean FROM and not WHERE
clause. If the ontology you are querying (as given in the FROM (NAMED)
clause) contains imports, then all imports will be loaded and the
axioms from the imported ontologies will be taken into account for
finding the query answers.

> It also raises an issue on the RIF side. RIF rules cannot be expressed in
> RDF. How would one add RIF rules to an entailement regime if we wanted to
> cover RIF? It might be a showstopper for that case:-(

In my total RIF naivity, I would assume you can say:

SELECT ?o FROM <http://example.org/myrules.rif> WHERE { :s :p ?o . }

Here I assume that myrules.rif contains the rules and references
(imports) for the relevant RDF graphs. In the RIF OWL compatibility
doc it says:

A RIF document that refers to (imports) RDF graphs and/or RDFS/OWL
ontologies, or any use of a RIF document with RDF graphs, is viewed as
a combination of a document and a number of graphs and ontologies.
This document specifies how, in such a combination, the document and
the graphs and ontologies interoperate in a technical sense, i.e., the
conditions under which the combination is satisfiable (i.e.,
consistent), as well as the entailments (i.e., logical consequences)
of the combination. The interaction between RIF and RDF/OWL is
realized by connecting the model theory of RIF [RIF-BLD] with the
model theories of RDF [RDF-Semantics] and OWL [OWL2-Semantics],
respectively.

In my example, I assume that myrules.rif is such a document as
mentioned above and you would query the RDF graphs pls the entailmens
that you get from the rules.

Birte

> Ivan
>
>
> --
>
> Ivan Herman, W3C Semantic Web Activity Lead
> Home: http://www.w3.org/People/Ivan/
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>



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Received on Thursday, 8 October 2009 10:35:09 GMT

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