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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 14:33:47 +0100
Cc: Ivan Herman <ivan@w3.org>, Andy Seaborne <andy.seaborne@hp.com>
Message-Id: <AF0259EE-FDFA-42F0-856C-FF8A8E189A7A@deri.org>
To: Birte Glimm <birte.glimm@comlab.ox.ac.uk>, SPARQL Working Group <public-rdf-dawg@w3.org>
p.s.: the proper URL for the references should have been:

1. http://www.w3.org/TR/rif-rdf-owl/#Importing_RDF_and_OWL_in_RIF

Also, FWIW, RIF has already defined some URIs for entailment regimes,  
we may think about adopting those,
cf.  http://www.w3.org/TR/rif-rdf-owl/#Specific_Profiles

best,
Axel

On 8 Oct 2009, at 14:05, Axel Polleres wrote:

>> > 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 13:34:22 GMT

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