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

From: Bernard Vatant <bernard.vatant@mondeca.com>
Date: Fri, 15 Dec 2006 12:17:57 +0100
Message-ID: <45828465.1050809@mondeca.com>
To: Richard Cyganiak <richard@cyganiak.de>, public-esw-thes@w3.org

Apologies for answering to myself ...

Just to point to a recent thread on mapping OWL ontologies to SKOS 
concepts, and the approach proposed by Jakob Voss, using SPARQL.

In this approach, there would be no direct relationship between the 
dog-as-class and the dog-as-concept, but functional rules such as:
"If a document has a subject of class "Dog", then index this document on 
concept "dogs"

PREFIX a: <some-ontology-of-animals>
PREFIX b: <my-library-classification-scheme>
CONSTRUCT { ?y         skos:subject     b:dogs }
WHERE {     ?x      a     a:Dog.
                     ?y      a      foaf:Document.
                     ?y     dc:subject     ?x. }

The advantage of this method is to be completely non-intrusive on both 
sides, since it avoids any declaration of direct relationship between 
a:Dog and b:dogs likely to entail unwanted consequences, e.g., on 
ontology species, as Dan points out.
And it will perform a precise functional task : index all my 
Fido-related resources (images, pedigree, family stories ...) in the 
"dogs" category.

Seems that this works for Ludwig Wittgenstein as well :-)

PREFIX a: <some-ontology-of-people>
PREFIX b: <my-library-classification-scheme>
CONSTRUCT { ?y         skos:subject     b:philosophy }
WHERE {     ?x      a     a:Philosopher.
                     ?y      a      foaf:Document.
                     ?y     dc:creator     ?x. }



Bernard Vatant a écrit :
> 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.
> Bernard
> 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
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Blog:    Leçons de Choses <http://mondeca.wordpress.com/>
Received on Friday, 15 December 2006 11:18:20 UTC

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