Re: OWL reasoning in rules - infinite domains and queries

Hi MAtt --

Another way of dealing with infinite, or very large finite, answers is this.

For many practical purposes, but without claiming to solve the Turing
Halting Problem, you can return say, the first 50 answers, and provide a
button with which the user can ask for more.

Also, I believe there is a construct in SPARQL that allows you to specify a
limit on the number of answers.

HTH,  -- Adrian

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Adrian Walker
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On 5/30/07, Matt Williams <matthew.williams@cancer.org.uk> wrote:
>
>
> Dear All,
>
> Following on from this discussion, and Ulrike's paper, if we have
> infinite (inferred) individuals, such as chains of fathers or Guards,
> and we query the ontology, what is returned?
>
> Would a query of the form Guard(x) or Father(x) return an infinite
> number of bindings? Or can we restrict it to "Known" individuals (which
> seems to be what Ulrike's paper suggests). Is this similar to what you
> can do with some of the SPARQL implementations (e.g. in Pellet) where
> you can allow/ disallow bNodes - or is this distinct (I suspect they're
> different - the rdf graph is not, I hope, infinite).
>
> Thanks,
>
> Matt
>
>
>
> Taowei David Wang wrote:
> >> Hmmm, I would like to see a small ontology which is necessarily
> infinite.
> >
> > As the movie 300 has made the Greek phalanx popular again, here is a
> small
> > ontology that contains a class that has only infinite models:
> >
> > Guard subclassOf ( (some shields.Guard) and ( <2 inverse(shields)) )
> > FirstGuard subclassOf ( Guard and ( <1 inverse(shields) )
> >
> > "Every Guard shields some Guard, and is in turn shielded by at most 1
> > Guard."
> >
> > "A FirstGuard is a Guard, and is not shielded by another."
> >
> > FirstGuard has no finite model, because it generates an
> > infinite number of Guards (every Guard needs to shield someone, and it
> > can't be the FirstGuard).
> >
> > The above example is found in this paper (Page 4, Sec 3):
> >
> > http://citeseer.ist.psu.edu/calvanese96finite.html
> >
> > other refs on topics of computing finite models in DL:
> >
> > http://citeseer.ist.psu.edu/710125.html
> >
> http://www.inf.unibz.it/~franconi/dl/course/articles/reasoning-survey.ps.gz
> >
> > I am sure others would chime in with newer papers, but these were
> helpful
> > to me.
> >
> > Cheers,
> >
> > Dave
> > ----
> >
> >
> >> I've just being looking with google, and found my own
> >> http://www.w3.org/TR/owl-test/dl-900-arith#description-logic-908
> >>
> >> which I believe hinges on
> >>     2*3*n = 5*n & n>0
> >>      implies n >= aleph0,
> >> but I am still trying to understand it.
> >>
> >> thanks for a pointer
> >>
> >> Jeremy
> >>
> >>
> >>
> >> --
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> >>
> >>
> >
>
> --
> http://acl.icnet.uk/~mw
> http://adhominem.blogsome.com/
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>
>