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Re: rdfs:class and rdfs:resource

From: Richard H. McCullough <rhm@cdepot.net>
Date: Fri, 9 May 2003 13:12:02 -0700
Message-ID: <002c01c31668$0ade3350$bd7ba8c0@rhm8200>
To: <www-rdf-interest@w3.org>, Dieter Köhler <dieter.koehler@philo.de>

Dieter
I agree with your discussion, but I think your Fido "class" is a bad
example.
Young & old versions of Fido should be considered the same instance
with some time-varying properties.

Dick McCullough
knowledge := man do identify od existent done;
knowledge haspart proposition list;

----- Original Message ----- 
From: "Dieter Köhler" <dieter.koehler@philo.de>
To: <www-rdf-interest@w3.org>
Sent: Friday, May 09, 2003 10:30 AM
Subject: RE: rdfs:class and rdfs:resource


>
> When re-reading my last posting, I got the impression that one sentence
was
> perhaps misleading:
>
> >But the following is, as far as I can see, *not* true:
> ><rdfs:Resource> <rdfs:subClassOf> <rdfs:Class> .
> >
> >In other words: There may exist instances of rdfs:Resources which are not
> >instances of rdfs:Class.  Or again in other words: Not everything must be
> >a class.
>
> The sentence
>    "But the following is, as far as I can see, *not* true:"
> should better read
>    "But the following is, as far as I can see, contingent:"
>
> The following explanation ("in other words ...") can remain
> unchanged.  What I was trying to say was that the statement
>
> <rdfs:Resource> <rdfs:subClassOf> <rdfs:Class> .
>
> does not necessarily follow from the axioms of [RDF Schema].  However, as
> far as I can see, this statement does not contradict the set of RDF Schema
> axioms. [RDF Schema] does not require that all Resources are Classes, but
> also does not state that there indeed exist Resources which are not
Classes.
>
> I also agree with Wolfram that "a (minimal) axiomatization might have a
> certain advantage over the current/previous versions of the RDF/RDFS
> specs", though my chain of reasons is different: Intuitively, I see no
> reason why
>
> <rdfs:Resource> <rdfs:subClassOf> <rdfs:Class> .
>
> should be excluded from RDF/RDFS.  RDF graphs are designed with
> extensibility in mind.  For example, consider the following graph which
> states that Fido is a dog and a dog is an animal:
>
> <foo:Animal> <rdfs:type> <rdfs:Class> .
> <foo:Dog> <rdfs:type> <rdfs:Class> .
> <foo:Dog> <rdfs:subClassOf> <foo:Animal> .
> <foo:Fido> <rdfs:type> <foo:Dog> .
>
> At first glance it seems reasonable to say that Fido is, ontologically
> speaking, an individual, while Dog and Animal are obviously classes.  Now
> consider that we want to add information about the young Fido and the old
> Fido to the above graph.  One way to do so is to add the following
statements:
>
> <foo:Fido> <rdfs:type> <rdfs:Class> .
> <foo:YoungFido> <rdfs:type> <foo:Fido> .
> <foo:OldFido> <rdfs:type> <foo:Fido> .
>
> and also perhaps:
>
> <foo:Fido> <rdfs:subClassOf> <foo:Dog> .  (= every instance of foo:Fido is
> also an instance of foo:Dog)
>
> So every Resource of a graph can be declared being a Class.  That suggests
> that the distinction between Resource and Class is for practical reasons a
> candidate for Okhams razor: The distinction between Resource and Class is
> superfluous and should be dropped in RDF/RDFS.
>
> Dieter Köhler
>
> Institute of Philosophy
> University of Karlsruhe
> Germany
>
>
>
Received on Friday, 9 May 2003 17:45:35 GMT

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