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

From: Bernard Vatant <bernard.vatant@mondeca.com>
Date: Fri, 15 Dec 2006 00:38:20 +0100
Message-ID: <4581E06C.8080104@mondeca.com>
To: Dan Brickley <danbri@danbri.org>, Richard Cyganiak <richard@cyganiak.de>
Cc: public-esw-thes@w3.org

Hi Richard, and Dan

To complete Dan's answer, something I'm munching over those days is that 
what's important with a RDF resource is more what one wants to use it 
for (its functionality), than what it stands for (its denotation). A 
skos:Concept is forged to index and search documents and other 
information resources (maybe even philosophers - see other thread about 
skos:subject), it's a librarian's tool. A rdfs:Class is forged to sort 
and find out stuff outthere by properties, it's a naturalist's tool, so 
to speak. So basically they are different tools for different purposes, 
and as such, should be kept distinct.

Now of course we have this permathread about how to link my-dog-concept 
to your-dog-class, if they are indeed kept distinct. I could again push 
the blank node connection here, but well ... In the same spirit than 
above, I prefer to ask : what do you want this for? Beyond the 
conceptual exercise, what is the use case? I ask because honestly, 
despite an interest for this question which is close to maniac 
obsession, I have not yet found a real-world, clear business use case 
where such a requirement is in the critical path.


Dan Brickley a écrit :
> 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


*Bernard Vatant
*Knowledge Engineering
*3, cité Nollez 75018 Paris France
Web:    www.mondeca.com <http://www.mondeca.com>
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Mail:     bernard.vatant@mondeca.com <mailto:bernard.vatant@mondeca.com>
Blog:    Leçons de Choses <http://mondeca.wordpress.com/>
Received on Thursday, 14 December 2006 23:38:26 UTC

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