Re: Question about skos:concept

Hi Antoine & Jyoti,

isn't it much more simple?

in OWL, "owl:Class is defined as a subclass of rdfs:Class" [1].

<rdfs:Class rdf:ID="Class">
  <rdfs:label>Class</rdfs:label>
  <rdfs:subClassOf rdf:resource="&rdfs;Class"/>
</rdfs:Class>

In RDFS you can read:

"2.1 rdfs:Resource All things described by RDF are called resources, and
are instances of the class rdfs:Resource. This is the class of
everything. All other classes are subclasses of this class.
2.2 rdfs:Class This is the class of resources that are RDF classes." [2]

<rdfs:Class rdf:about="http://www.w3.org/2000/01/rdf-schema#Class">
  <rdfs:isDefinedBy rdf:resource="http://www.w3.org/2000/01/rdf-schema#"/>
  <rdfs:label>Class</rdfs:label>
  <rdfs:comment>The class of classes.</rdfs:comment>
  <rdfs:subClassOf rdf:resource="http://www.w3.org/2000/01/rdf-schema#Resource"/>
</rdfs:Class>

That's why skos:Concept does not need a subClassOf rdfs:Resource, it is
inherited.
Class hierarchy is:

rdfs:Resource
    rdfs:Class
       owl:Class
          skos:Concept

Hope this helps,

Thomas

[1] http://www.w3.org/TR/owl-ref/#Class
[2] http://www.w3.org/TR/rdf-schema/#ch_resource


Antoine Isaac schrieb:
> Hi Jyoti,
>
> Indeed there is no explicit subClassOf relationship between
> skos:Concept and rdfs:Resource.
>
> But it is implicitly here: if I'm not mistaken, an RDFS/OWL inference
> engine can get it from the RDFS and OWL semantics, especially using
> [1] which has the following axiom:
> If x is in IC then <x, I(rdfs:Resource)> is in IEXT(I(rdfs:subClassOf))
> ( where IC = ICEXT(I(rdfs:Class)) )
>
> Cheers,
>
> Antoine
>
> [1] http://www.w3.org/TR/rdf-mt/#vocabulary_entail
>
>
>
>> Hello all,
>>
>> I am seeking a clarification about skos:concept.
>>
>> <rdf:Description rdf:about="#Concept">
>> <rdfs:label xml:lang="en">Concept</rdfs:label>
>> <rdfs:isDefinedBy rdf:resource="http://www.w3.org/2004/02/skos/core"/>
>> <skos:definition xml:lang="en">An idea or notion; a unit of
>> thought.</skos:definition>
>> <!-- S1 -->
>> <rdf:type rdf:resource="http://www.w3.org/2002/07/owl#Class"/>
>> </rdf:Description>
>>
>> 1.) At present, skos:concept is defined as an instance of owl:class
>> (and hence, an instance of rdfs:resource). However, I do not see any
>> "explicit" subClassOf relationship between skos:concept and
>> rdfs:resource. Am I correct in assuming that such a relationship does
>> not exist?
>>
>> 2.) If the answer to question# 1 is yes, could you please explain
>> (preferably with an example) why such an assertion was not included
>> in the specification?
>>
>> Thank you in advance for your replies!
>>
>> Cheers,
>> - Jyoti
>
>
>


-- 
Thomas Bandholtz, thomas.bandholtz@innoq.com, http://www.innoq.com 
innoQ Deutschland GmbH, Halskestr. 17, D-40880 Ratingen, Germany
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Received on Monday, 3 August 2009 17:45:17 UTC