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Re: Are skos:Concept and rdfs:Class disjoint?

From: Dan Brickley <danbri@danbri.org>
Date: Thu, 14 Dec 2006 19:09:10 -0300
Message-ID: <4581CB86.4030308@danbri.org>
To: Richard Cyganiak <richard@cyganiak.de>
Cc: public-esw-thes@w3.org

Richard Cyganiak wrote:
>
> Another quick question:
>
> Can a skos:Concept be an rdfs:Class at the same time? For example, if 
> I have in my taxonomy a skos:Concept ex:Dog, then would it be OK to 
> also make this an rdfs:Class and say something like this?
>
>     :ginger a ex:Dog .
>
> I suppose the answer is no because an RDFS class is something else 
> than a taxonomic concept. I'm interested in an explanation that is a 
> bit less hand-wavy than "it's something else."
How about: "I guess we could, but it would upset the OWL-DL constituency 
because it intermingles the ontological and instance data layers"?

Some but far from all SKOS Concepts are, more or less, categories, ie. 
classes. Whether we indicate this in the Semantic Web by simple identity 
(ie. have the self-same thing simply be a Class and a Concept) , ... or 
whether we indicate this by named relationship (util:hasClass), is I 
think something still up for discussion. It is related to the question 
of how we indicate which SKOS Concepts "stand for" specific individuals, 
eg. a person, a place, or  event. I would be dissapointed if we answered 
those two questions separately, since it is the same core question: how 
does the (indirected, lowercase-r reified) SKOS worldview relate to the 
vanilla RDF/OWL worldview. The former is in terms of concepts, eg. 
the-concept-of-dogs, the-concept-of-fido; the latter is in terms of 
named classes, relationships and members of those classes: the class 
Dog, and the individual "fido" who is a thing in the class "Dog". In the 
RDF view, ... we get to ascribe arbitrary properties to Fido. In the 
SKOS view, we need to be careful when talking about individuals, since a 
SKOS concept for fido has different properties (creation date, for eg) 
than the thing it is the concept of. This is clearer in the case of 
individuals than in the case of classes.

cheers,

Dan
Received on Thursday, 14 December 2006 22:09:27 GMT

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