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Re: rdfs:isDefinedBy (Was Re: Representing DCMI semantics asRDFschemas versus Web pages)

From: Daniele Capursi <capursi@sword.it>
Date: Mon, 10 Jun 2002 15:31:35 +0200
Message-ID: <001601c21083$27819880$2c00000a@renoir>
To: "Dave Reynolds" <der@hplb.hpl.hp.com>, "Patrick Stickler" <patrick.stickler@nokia.com>
Cc: "RDF Interest" <www-rdf-interest@w3.org>

Thank you very much! Your explanations were concise but complete and very useful!
Please let me ask you something that might be well-known, but that I don't know (see at the end of this email).

> > The higher level of RDF validation is RDF Schema validation, which tests
> > that range and domain constraints match the subjects and objects of
> > actual statements. The W3C RDF validator does not perform such checks.
> Actually, AFAIK, such constraints can't be expressed in pure RDFS. So it is
> entirely reasonable for the W3C validator to not perform checks for them. An
> application could choose to interpret RDFS domain/range declarations as somehow
> exclusive and checkable but that is not part of the RDFS specification and so
> should not be part of the W3C validator.
> To (ab)use Graham's recent example on the multiple rdf:type issues. If I have an
> RDF schema that includes:
>    ex:transport  rdf:type   rdfs:Property .
>    ex:transport  rdfs:range ex:MeansOfTransport .
> and I then check an RDF file containing:
>    urn:me      ex:transport  urn:Dobbin .
>    urn:Dobbin  rdf:type      foo:Horse .
> Then all I can conclude is "that is interesting, urn:Dobbin must be both a
> foo:Horse and an ex:MeansOfTransport". This might or might not be reasonable. 
> If we then encounter the declaration:
>    ex:MeansOfTransport rdfs:subClassOf ex:MechanicalDevice .
> then we would conclude that urn:Dobbin is also an ex:MechanicalDevice. 
> Given the suggestive names then as humans we might be less happy with something
> being both a Horse and a MechanicalDevice but for RDFS processing there is no
> reason to believe something can't be both.

So what's the use of an RDF schema?
How can I prevent using a property in an improper way? 
e.g. I want that it's possible to say that a thing is an Author only if that thing is a Human. I don't want to say that, since A is an Author, A must be a human! That's not _validating_ (i.e. checking), that's inferring (i.e. saying new things)!
So what type of constraint can be _validated_, according to w3c?

Thanks a lot in advance.

Daniele Capursi
Received on Monday, 10 June 2002 09:31:34 UTC

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