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Re: Possible semantic bugs concerning domain and range

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Fri, 25 Oct 2002 10:16:54 +0100
Message-ID: <15801.3078.295653.750916@merlin.horrocks.net>
To: pat hayes <phayes@ai.uwf.edu>
Cc: www-webont-wg@w3.org

On October 24, pat hayes writes:
> 
> >There may be pragmatic/implementation reasons to go for implies
> >semantics in all cases:
> >
> >- it can only lighten the burden on implementors as there will be
> >fewer kinds of logical entailment to worry about.
> >
> >- the cost isn't very great as implied functionality, transitivity
> >etc. due to strange constraints on possible models doesn't seem like
> >it would be of great interest.
> >
> >- it would satisfy Pat's complaint that logically entailed range and
> >domain restrictions are positively harmful.
> 
> But it would fail to satisfy the RDFS requirement that subClassOf and 
> subPropertyOf are transitive. We could of course just add this as an 
> ad-hoc semantic requirement, but that seems very tacky.

I'm not sure what your point is here. Are you concerned as to whether
subClassOf and subPropertyOf are implicitly instances of
owl:TransitiveProperty? I do not believe that this would not be a
valid Fast OWL inference (or at least not a question one could ask).

> Given the option between all IF and all IFF, I think the all-IFF 
> option is more coherent. But I would prefer a more tailored solution, 
> as you know.

I prefer all IF for the reasons I have mentioned, in particular the
possible extra burden on implementors. E.g., it isn't clear that these
entailments can be reduced to satisfiability and still stay within OWL
Lite (it might be possible, but not via the reductions we have
mentioned up to now as these rely on nominals), so these entailments
might make it harder to implement a complete OWL Lite reasoner.

Ian


> 
> Pat
> 
> 
> 
> >Ian
> >
> >
> >On October 15, Jeremy Carroll writes:
> >>
> >>  Summary: attempt to collect arguments about this issue.
> >>  (Also added justification for uniformity, and a new argument about mutually
> >>  entailing ontologies).
> >>
> >>  >Range
> >>  >Domain(P,C) implies/iff (forall x,y P(x,y) -> C(x))
> >>
> >>  >TransitiveProperty(P) implies/iff (forall x,y,z (P(x,y) ^ P(y,z)) 
> >>-> P(x,z))
> >>  >SymmetricProperty(P) implies/iff (forall x,y P(x,y) -> P(y,x))
> >>  >FunctionalProperty(P) implies/iff (forall x,y,z (P(x,y) ^ P(x,z)) -> y=z)
> >>  >InverseFunctionalProperty(P) implies/iff (forall x,y,z (P(y,x) ^
> >>  >P(z,x)) -> y=z)
> >>  >inverseOf(P,Q) implies/iff (forall x,y P(x,y) -> Q(y,x))
> >>
> >>  I hear Dan, Jos, myself, Peter and Ian being able to go either way here.
> >>
> >>  There seem to be various arguments:
> >>
> >>  - treat them all the same
> >>  (unarticulated)
> >>   Less difficult for implementors,. less difficult to document, 
> >>less difficult
> >>  to learn. I suspect the Guide would be shorter with iff semantics.
> >>
> >>  - implies only
> >>   Few implementation would actually implement iff.
> >>   (However most of the implementors in the group seem to have come 
> >>round to the
> >>  possibility of implementing iff)
> >>
> >>  - natural usage
> >>   Pat (so far unsupported) has opinions about natural usage that 
> >>split domain,
> >>  range and inverse off as intensional (implies) and the others as extensional
> >>  (iff).
> >>
> >>  - rdf datatyping
> >>   I think this argument is now dead - some versions of 
> >>rdf:datatyping requried
> >>  intensional reading of rdf:range.
> >>
> >>  - possibility of identifying identical ontologies (new argument)
> >>   With extensional semantics then ontologies using these with identical
> >>  semantics entail one another. With intensional semantics then it is not the
> >>  case e.g.
> >>
> >>  <owl:FunctionalPropery rdf:ID="a">
> >>     <owl:inverse rdf:resource="#b" />
> >>  </owl:FunctionalProperty>
> >>
> >  >
> >  > <owl:InverseFunctionalPropery rdf:ID="b">
> >  >    <owl:inverse rdf:resource="#a" />
> >  > </owl:InverseFunctionalProperty>
> >  >
> >  > either have identical meaning or not.
> >  > Seems potentially useful, to say that they do have identical meaning.
> >>
> >>  - argument by authority
> >>  iff we take this style of argument seriously
> >>
> >>  - surprising entailments
> >>  An empty property is necessarily transitive, functional, inversefunctional,
> >>  its own inverse,  etc.
> >>
> >>
> >>  I think consistency is what I feel strongly about.
> >>
> >>  Jeremy
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> 
> 
> -- 
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Received on Friday, 25 October 2002 05:17:03 GMT

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