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Re: Rules WG -- draft charter -- NAF

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Tue, 18 Nov 2003 14:23:41 -0500 (EST)
Message-Id: <20031118.142341.132597007.pfps@research.bell-labs.com>
To: stefan@ISI.EDU
Cc: www-rdf-rules@w3.org

From: Stefan Decker <stefan@ISI.EDU>
Subject: Re: Rules WG -- draft charter -- NAF
Date: Tue, 18 Nov 2003 18:13:06 +0000

> Peter,
> 
> >Huh?  How are mediums for the exchange of data significantly different from
> >logics?  Do you really mean to have rules work on the syntax of RDF?
> >
> >To me, a rule that works on the syntax of RDF would be something like:
> >
> >if   <rdf:Description rdf:type="?x" ??a>??y</rdf:Description>
> >then <?x ??a>??y</?x>
> >
> >which converts some RDF/XML syntax into a shorthand form with the same
> >meaning.
> That I meant was something working on the RDF graph, not the XML syntax.
> The RDF graph might be syntax again for something else (e.g., an OWL Ontology).

Well, I am still confused as to how this would work.  How would one
interpret a rule on an RDF graph without reference to the RDF (or some
other) semantics?

> > > > > If we want to take the semantics into account, let us try to define
> > > > what the
> > > > > problem is, and look at which part of the problem a rule language can
> > > > > solve, and
> > > > > how to incorporate solutions for the other problems.
> > > > > Do you have a definition of the problem you are trying to solve?
> > > >
> > > >No, but I'm not trying to restrict the possible solutions, either.  All
> > > >I've been saying is that CWA and other circumscriptive notions have a
> > > >decided cost in very many settings.
> > > Definitely - if we talk about circumscription for FOL theories.
> > > Non-monotonic operators for datalog are much cheaper.
> > > Lets find out what we want.
> >
> >Agreed, but then pronouncements like ``CWA is easy'' should not be allowed
> >because we don't yet know whether the problem will admit a solution where
> >CWA is indeed easy.
> I was just talking about CWA on a graph.

Hmm.  

What would the CWA make of the following graph?

rdf:type rdf:type rdf:Predicate .
rdf:type rdfs:domain rdfs:Resource . 
ex:john rdf:type ex:Person .

Would it require that there be no domain element for, for example,
rdfs:Class?

What would the CWA make of the folowing graph?

ex:Student rdfs:subClassOf _:x .
_:x rdf:type owl:Restriction .
_:x owl:onProperty ex:sid .
_:x owl:allValuesFrom xsd:integer .

In particular, would it require that there be no domain element for _:y in
the following.

_:y rdf:type owl:Restriction .
_:y owl:onProperty ex:sid .
_:y owl:allValuesFrom rdfs:Literal .

I forsee many similar problems in applying a CWA without use of semantics. 

[...]

peter
Received on Tuesday, 18 November 2003 14:25:42 UTC

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