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RE: Datatype was RE: Confusion about Collections

From: Shelley Powers <shelleyp@burningbird.net>
Date: Tue, 26 Nov 2002 06:54:15 -0600
To: "Patrick Stickler" <patrick.stickler@nokia.com>, <fmanola@mitre.org>
Cc: <www-rdf-comments@w3.org>, "Brian McBride" <bwm@hplb.hpl.hp.com>
Message-ID: <AOEKLHGMHIHGNIBEDMNMOELBDFAA.shelleyp@burningbird.net>

> 
> 
> 
> [Patrick Stickler, Nokia/Finland, (+358 40) 801 9690, 
> patrick.stickler@nokia.com]
<snip>

> > >
> > > Shelley,
> > >
> > > You can specify the datatype range of a property using rdfs:range to
> > > accomplish this. E.g.
> > >
> > >    my:dateProperty rdfs:range xsd:date .
> > >
> > > And this asserts that all values of my:dateProperty are expected
> > > to be of type xsd:date.
> > >
> > > Cheers,
> > >
> > > Patrick
> > 
> > 
> > That's good to know Patrick. I must have missed this in the 
> vocab document.
> > And one can also assume, then, that people who create instances of a
> > vocabulary (a specific document) can't override the data type 
> that's shown
> > in the schema. Is that correct?
> 
> In a sense, yes, in that if they do they will introduce a contradiction
> into the graph. But this is of course true of any RDF range, not just
> for datatyping. E.g. if one asserts that
> 
>    my:property rdfs:range foo:Blargh .
> 
> and someone else asserts
> 
>    my:property rdfs:range bar:Foodle .
> 
> and if it is known (e.g. by OWL assertions) that the classes
> foo:Blargh and bar:Foodle have disjunct membership, then there
> arises a conflict between the two range assertions, and its
> resolution will likely be based on some concept of authority
> (though RDFS doesn't explicitly say how to do this).
> 
> Likewise, if one asserted
> 
>    my:property rdfs:range foo:Blargh .
> 
>    some:Thing my:property _:x .
>    _:x rdf:type bar:Foodle .
> 
> then an RDF reasoner may infer
> 
>    _:x rdf:type foo:Blargh .
> 
> then again if the two classes have disjunct membership, these two 
> type assertions  for _:x conflict with each other and that
> conflict may be used by an application as the basis for type
> checking, taking the explicit range assertion as primary.
> 
> Note that with RDF datatyping
> 
>    some:Thing some:property "LLL"^^some:Datatype .
> 
> implies
> 
>    "LLL"^^some:Datatype rdf:type some:Datatype .
> 
> though we can't actually express the latter as literals are not allowed
> to be subjects, but the semantics are "understood" -- i.e. that 
> the thing denoted by a typed literal node is a member of the
> value space (the class extension) of the datatype class specified
> in the typed literal.
> 
> I hope the above is helpfull.
> 
> Cheers,
> 
> Patrick
> 
Yes, Patrick. This has been very helpful. I appreciate your clarification.

Shelley

P.S. Is this same discussion in the documents, and did I just miss it? 
Received on Tuesday, 26 November 2002 07:55:31 GMT

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