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Re: [RDF+OWL] Problem with coreifying RDFS entailment embedding

From: Gary Hallmark <gary.hallmark@oracle.com>
Date: Tue, 03 Mar 2009 21:40:27 -0800
Message-ID: <49AE144B.7050400@oracle.com>
To: Jos de Bruijn <debruijn@inf.unibz.it>
CC: RIF <public-rif-wg@w3.org>
rdfs:Resource is kind of like java.lang.Object.  My product supports 
?v#Object for expert use in rules, but we discourage it.  Rules that 
truly apply to every object/resource are very rare.  I support option #1 
as the least objectionable of the 3.

Jos de Bruijn wrote:
> While trying to prove that the RIF Core version of the RDFS embedding I
> came up with [1] is correct, I found out that it is not.  In fact, I
> believe it is not possible to embed all RIF-RDFS combinations into RIF
> Core in a straightforward manner.  The problem is with rdfs:Resource.
> According to the semantics, every object in the domain is in the class
> extension of rdfs:Resource. This is naturally expressed using the rule
> Forall ?x (?x[rdf:type -> rdfs:Resource])
>
> However, this rule is not safe.  I see three ways of dealing with this
> problem:
>
> 1) disallow using rdfs:Resource in the rules and in RDF triples that are
> not of the form xxx rdf:type rdfs:Resource in the embedding
>
> 2) extending the embedding to define rules for all predicate symbols
> appearing in the rule set, e.g., if ex:p is a binary predicate, we add
> the rules
> Forall ?x ?y (?x[rdf:type -> rdfs:Resource] :- ex:p(?x,?y))
> Forall ?x ?y (?y[rdf:type -> rdfs:Resource] :- ex:p(?x,?y))
>
> 3) we drop the requirement of the rules being safe
>
> I would prefer option 1, because option 2 would make the embedding very
> complicated and I guess it is desirable to have the embedding in RIF
> Core (ruling out option 3).
>
> Best, Jos
>   
Received on Wednesday, 4 March 2009 05:41:20 GMT

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