Re: range, domain: Conjunctive AND disjunctive semantics both supportable

On Fri, 29 Sep 2000, Graham Klyne wrote:

> At 10:21 AM 9/29/00 +0100, Jan Grant wrote:
> >and loosely:
> >
> >P has a range of (a member of the union of A and B)
> >
> >         A --[rdfs:subclassOf]-> anon:C
> >         B --[rdfs:subclassOf]-> anon:C
> >         P --[rdfs:range]-> anon:C
> >
> >(give anon:C a real URI if you prefer).
> >
> >Are there problems with this scheme?
> 
> I like the approach.
> 
> 
> I don't know if it's a _problem_, but I don't think this actually allows 
> one to validate OR infer much in an open-world environment.  E.g. the above 
> statements don't allow us to infer from:
>         S --P--> O
> the truth or falsity of any of the following:
>         O --rdf:type--> A
>         O --rdf:type--> B
>         O --rdf:type--> D
> 
> 
> Similarly, they don't allow us to validate a statement like:
>         S --P--> O
> where
>         O --rdf:type--> D
> 
> 
> I guess what it does tell us is that
>         S --P--> O
> where
>         O --rdf:type--> A
> or
>         O --rdf:type--> B
> is definitely valid.

Yep. By 'validation' I meant the last case.

I get the feeling that everyone agrees that the disjuntive semantics is
"weaker": at least, in the standard picture of RDF usage where the
closed-world assumption doesn't hold.

Being able to model disjunctive semantics like this, however, should
suffice for those people who need it. _Application_ level uses of RDF
will obviously involve attaching additional semantics (the "F" stands
for "Framework", remember) which might well allow stronger
interpretations of the disjuntive case.

-- 
jan grant, ILRT, University of Bristol. http://www.ilrt.bris.ac.uk/
Tel +44(0)117 9287163 Fax +44 (0)117 9287112 RFC822 jan.grant@bris.ac.uk
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