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Re: [TF-Ent] RIF Core Entailment section

From: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
Date: Fri, 12 Mar 2010 00:31:47 +0000
Message-ID: <492f2b0b1003111631o50931b2xe0972a4d63227ed9@mail.gmail.com>
To: Chimezie Ogbuji <ogbujic@ccf.org>
Cc: Ivan Herman <ivan@w3.org>, SPARQL Working Group WG <public-rdf-dawg@w3.org>, Axel Polleres <axel.polleres@deri.org>, Sandro Hawke <sandro@w3.org>
On 11 March 2010 17:30, Chimezie Ogbuji <ogbujic@ccf.org> wrote:
> Comments below
>
> On 3/10/10 9:35 AM, "Birte Glimm" <birte.glimm@comlab.ox.ac.uk> wrote:
>> Yes, that's what I mean. As I understand it SG or sk(SG) is the graph
>> you get from the triples and it knows nothing about the rule set. We
>> would have to specify a vocabulary that is the union of the vocabulary
>> of SG/sk(SG) and the vocabulary of the import closure of the
>> referenced rule sets. That's not difficult to do, we should just add
>> it.
>
> Do we even need this condition for RIF Simple entailment? The vocabulary of
> the generalized RDF graphs entailed by the combination (strongly, safe RIF
> Core document,sk(SG)) 'include' the vocabulary of SG and the corresponding
> RDF names in the RIF document (this also includes its import closure).  Is
> there an example that demonstrates needing anything more than requiring that
> the RDF triples sk(P(BGP)) are ground and RIF-Simple entailed by the
> combination?

When you don't need C2 because you'll anyway only entail a finite
number of triples (modulo bnode identifier), then that's not
necessary. I guess strongly safe gives you just that.
As soon as you add C2, you want to have a vocabulary does cover enough
so that you don't exclude triples that are entailed and that you would
like to keep.

Birte

> I have updated the Simple RIF Core entailment regime with a paragraph that
> briefly discusses this.  Going back to your example below
>
> .. if we have SG:
> ex:a a ex:b .
> rif-rdf:usesRuleset ex:rules.rif .
>
> with ex:rules.rif:
> ex:b(x) -> ex:c(x)
>
> and query:
>
> SELECT ?x WHERE { ?x a ex:c }
>
> Then I (too) would expect to get ?x/ex:a
>
> In this case sk(P(BGP)) is the same as P(BGP):
>
> ex:a a ex:c
>
> And the entailed, generalized graph EG would be (a proper superset of SG):
>
> ex:a a ex:b .
> ex:a a ex:c
>
> In which case P(BGP) is a subgraph of EG.  So, there is no need to
> explicitly restrict the bound names.
>
>
> -- Chime
>
>
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-- 
Dr. Birte Glimm, Room 306
Computing Laboratory
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Received on Friday, 12 March 2010 00:32:27 GMT

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