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OWL-RL (OWL 2 Profiles)

From: Dimitrios Koutsomitropoulos <kotsomit@hpclab.ceid.upatras.gr>
Date: Tue, 2 Dec 2008 17:33:04 +0200
To: <public-owl-dev@w3.org>
Message-ID: <002701c95493$44a79990$cdf6ccb0$@ceid.upatras.gr>

Could please somebody explain what has happened to OWL-R DL and OWL-R Full?
>From my understanding, OWL-R DL used to be pure DLP, while OWL-R Full allows
all constructs and has no constraints on syntax, but rule-based reasoning
remains complete only under weaker semantics (I think this profile was
equivalent to OWLim's OWL Horst). How is this new OWL-RL compared to the
other two?

Regards,
Dimitrios 

> -----Original Message-----
> From: public-owl-dev-request@w3.org [mailto:public-owl-dev-
> request@w3.org] On Behalf Of Dimitrios Koutsomitropoulos
> Sent: Friday, November 07, 2008 10:33 PM
> To: public-owl-dev@w3.org
> Subject: RE: Punning between properties types
> 
> 
> Bijan, thanks for your prompt reply. Please find my
> comments/understanding
> below:
> 
> > -----Original Message-----
> > From: public-owl-dev-request@w3.org [mailto:public-owl-dev-
> > request@w3.org] On Behalf Of Bijan Parsia
> > Sent: Friday, November 07, 2008 9:52 PM
> > To: Dimitrios Koutsomitropoulos
> > Cc: public-owl-dev@w3.org
> > Subject: Re: Punning between properties types
> >
> >
> > On 7 Nov 2008, at 17:53, Dimitrios Koutsomitropoulos wrote:
> >
> > > Hello all,
> > >
> > > Regarding the punning issue in OWL 2, I notice than in the new OWL
> > > 2 semantics document [1], in the changes summary,  punning has been
> > > disallowed between object and data properties.
> > >
> > > The relevant issue [2] is resolved based on the fact that “there
> > > are no use-cases” or “we don’t know how to do it”.
> >
> > No no no! Some people might believe these things but I certainly and
> > vocally don't ;) There are plenty of use cases and we do know how to
> > do it. The problem is that in order to disambiguate certain punning
> > cases in RDF triples we need to introduce new logical vocabulary
> > (since there is no context for the occurrence of a URI node...there's
> > only one in the whole graph). Some people (most prominently, HP)
> > objected to this. So, the compromise was to through out all sorts of
> > punning that in the RDF serialization required new vocabulary.
> >
> > > From this I understand that an <owl:objectProperty> cannot be
> > > treated as an <owl:datatypeProperty> and vice-versa.
> >
> > This is true.
> >
> > > However what is the deal with <rdf:property> ?
> >
> > There's no such thing, really, in OWL 2 non-full. Every property is
> > required to be one or the other (or an annotation propery).
> 
> So the only legal way for an <rdf:property> to be treated by an OWL 2
> tool,
> is to consider the ontology as OWL 2 full. Where I presume this
> property
> would be considered *both* as object- and data- and not punned. But it
> would
> still be syntactically correct, whereas in OWL 2 DL it is not allowed.
> 
> >
> > > When an rdf ontology is loaded by a reasoner or an application ,
> > > how should it treat a generic <rdf:property>?
> >
> > The spec does not say. In the extreme case it could reject the
> > ontology as malformed (for DL reasoning). Or it could ask the user.
> > Or it could attempt some repair using heuristics. Or it could pass it
> > on to an OWL Full mode (if there is such).
> 
> This fullness should imply that no reasoning is to be attempted?
> >
> > > I see three options:
> > >
> > > -          Such properties should be totally ignored (or should not
> > > exist all along)
> > > -          Should be considered only of a fixed type (either data -
> > > or object-)
> > > -          Should be punned based on their use
> >
> > The latter is possible in some cases, but not in every case. A simple
> > example, suppose you have P and C as terms in your ontology and the
> > declarations:
> >
> > ObjectProperty(P)
> > DataProperty(P)
> > Class(C)
> > Datatype(C)
> >
> > Now, what do you do with the expression P some C? Is it an
> > objectproperty somevalues from or a dataproperty somevaluesfrom, or
> > both? More to the point what if you want to say that something was P
> > (object) some C and P (data) all not (datatype) C?
> >
> > Those parens don't work in RDF.
> >
> > Now, in many cases we can make good guesses. Tools will have to come
> > up with them :)
> 
> Therefore, punning on the types of properties *can* work, at least in
> some
> cases, without fullness. For example for those where there are no
> restrictions on such properties. Shouldn't this part be considered by
> the
> OWL 2 spec?
> 
> 
> >
> > > Latest Protégé 4 (b. 103) seems to follow the last option, with
> > > which I personally agree. This is also supported by the latest
> FaCT+
> > > + (1.2.0)
> >
> > There is another option: "Determined based on what we can glean of
> > their use".
> >
> > > However Pellet 2.0 throws exceptions. Is this a bug or a feature,
> > > considering the above resolution?
> >
> > It is conforming. The specs don't say what to do with non-conforming
> > ontologies. I'd say that one would hope that the tools will do better
> > than throw an exception.
> Is there a way to guide Pellet to "overcome" such properties? It just
> seems
> to consider such properties only as object ones and rejects the
> ontology
> when it finds out that they (may) reference data values (I should have
> posted this elsewhere but I couldn't help it, sorry)
> 
> >
> > > In addition, should Protégé 4 and FaCT++ drop this feature?
> 
> What about Protégé and FaCT++ then? Are they not conforming?
> 
> > > Finally, is this perhaps an issue different than punning between
> > > properties (i.e. has nothing to do)?
> >
> >
> > It's related.
> 
>  Same with me. Therefore, the WG should look into this. Or at least
> specify
> what apps *may* do in such cases.
> 
> Dimitrios
> 
> 
> 
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Received on Tuesday, 2 December 2008 15:34:05 GMT

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