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Re: Possible semantic bugs concerning domain and range

From: Ian Horrocks <horrocks@cs.man.ac.uk>
Date: Thu, 17 Oct 2002 18:39:25 +0100
Message-ID: <15790.62925.811830.310168@merlin.horrocks.net>
To: Jeremy Carroll <jjc@hpl.hp.com>
Cc: www-webont-wg@w3.org

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.

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
> 
> 
> 
> 
> 
> 
>   
Received on Thursday, 17 October 2002 13:39:36 GMT

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