W3C home > Mailing lists > Public > www-rdf-interest@w3.org > May 2004

interpretation of instance and subclass

From: Burkett, Bill <WBurkett@modulant.com>
Date: Fri, 7 May 2004 18:27:10 -0400
Message-ID: <9B380E0FEF2D3149B5F02D7609352C36010DA367@ch1ex1.pdit.int>
To: <www-rdf-interest@w3.org>

I posed a question to an OWL discussion list concerning interpretation of classes that are both instances/members of and subclasses of the same class.  A colleague there suggested that I redirect the question to this list.  (I'm sure this has been a topic of discussion here before, but I'm new and a brief search of the archives didn't turn up anything that was dead-on-topic.)

Thanks -- Bill

Bill Burkett wrote:
>There are several places in the RDF/RDFS/OWL documentation where a class is defined as both 
>an instance of and a subclass of a parent class, e.g.:
>	<rdfs:Class rdf:about="http://www.w3.org/2000/01/rdf-schema#Datatype">
>	  <rdfs:isDefinedBy rdf:resource="http://www.w3.org/2000/01/rdf-schema#"/>
>	  <rdfs:label>Datatype</rdfs:label>
>	  <rdfs:comment>The class of RDF datatypes.</rdfs:comment>
>	  <rdfs:subClassOf rdf:resource="http://www.w3.org/2000/01/rdf-schema#Class"/>
>	</rdfs:Class>
>Similarly, owl:Class is defined as both an instance of and subclass of rdfs:Class.  
>I am trying to understand what this really means and what the ramifications are.  A fundamental 
>problem I'm having is understanding the transtivity of membership.  If m is an instance/member 
>of class M, and M is both an instance/member of and a subclass of class C, then transitivity 
>would state that m is also an instance/member of C (because M is a subclassOf C).  This would 
>further imply that since M is also an instance of C, m and M are somehow peers as instances of 
>C - which I find odd and hard to understand/reconcile.
Received on Friday, 7 May 2004 18:41:03 UTC

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