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

From: Jos de Bruijn <debruijn@inf.unibz.it>
Date: Tue, 10 Mar 2009 10:28:57 +0100
Message-ID: <49B632D9.4010606@inf.unibz.it>
To: Dave Reynolds <der@hplb.hpl.hp.com>
CC: RIF <public-rif-wg@w3.org>


Dave Reynolds wrote:
> 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).
> 
> Something like option (1) seems like the best solution to me. However,
> wouldn't you also need permit triples of the form:
> 
>     xxx rdfs:subClassOf rdfs:Resource

I suppose such triples would not do any harm, so we could allow them.
I was not aware, however, that people actually used such statements in
practice.

Jos

> 
> ?
> 
> Dave

-- 
+43 1 58801 18470        debruijn@inf.unibz.it

Jos de Bruijn,        http://www.debruijn.net/
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Received on Tuesday, 10 March 2009 09:29:45 GMT

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