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

From: Axel Polleres <axel.polleres@deri.org>
Date: Thu, 8 Oct 2009 14:05:24 +0100
Cc: "Ivan Herman" <ivan@w3.org>, "Seaborne, Andy" <andy.seaborne@hp.com>, "SPARQL Working Group" <public-rdf-dawg@w3.org>
Message-Id: <F0EFD877-5FA8-41B8-8A2E-68FC2A9B48F4@deri.org>
To: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
> > 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 . }
>

I was thinking that one viable alternative would be viewing RIF  
rulesets rather at the
level of *defining* an entailment regimes in their own right,
thus having them more at the level of service descriptions...

So, one could define say in SD

    myEndpoint sd:EntailmentRegime sd:rdfs .

    myEndpoint sd:EntailmentRegime sd:owl .

or, alternatively:

     myEndpoint sd:EntailmentRegime <http://example.org/myCustomEntailmentRules.rif 
 >

where <http://example.org/myCustomEntailmentRules.rif> points to a RIF  
ruleset, describing the supported entailment rules.

Alternatively, we could also allow to use

  owl:imports to refer to RIF rulesets (just as RIF allows in its own  
imports directive to refer to OWL ontologies, cf. [1]

Axel

1. http://www.w3.org/2005/rules/wiki/SWC#Importing_RDF_and_OWL_in_RIF


On 8 Oct 2009, at 11:34, Birte Glimm wrote:

> 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/
> > mobile: +31-641044153
> > PGP Key: http://www.ivan-herman.net/pgpkey.html
> > FOAF: http://www.ivan-herman.net/foaf.rdf
> >
>
>
>
> --
> Dr. Birte Glimm, Room 306
> Computing Laboratory
> Parks Road
> Oxford
> OX1 3QD
> United Kingdom
> +44 (0)1865 283529
>
Received on Thursday, 8 October 2009 13:06:00 GMT

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