W3C home > Mailing lists > Public > www-rdf-comments@w3.org > July to September 2002

Re: RDF Issue rdfs-clarify-subClass-and-instance

From: pat hayes <phayes@ai.uwf.edu>
Date: Mon, 26 Aug 2002 00:35:48 -0700
Message-Id: <p05111b06b98f8a75d643@[]>
To: Piotr Kaminski <piotr@ideanest.com>
Cc: www-rdf-comments@w3.org

>A minor nitpick:
>From: "pat hayes" <phayes@ai.uwf.edu>
>>  What makes something a class is just that it has some
>>  things in it (that is, in its extension)
>A class can have an empty extension.  If I say:
>pk:EmptyClass rdf:type rdfs:Class
>And there are no statements like this anywhere in my model:
>_:anything rdf:type pk:EmptyClass
>Then pk:EmptyClass still qualifies as a class, right?
>So I think it's more accurate (and perhaps simpler?) to say, just like in
>the Model Theory:
>A resource is a class if and only if it has rdf:type rdfs:Class (implicitly
>or explicitly).
>Every resource that is the object of an rdf:type statement is implicitly of
>rdf:type rdfs:Class.
>Any resource can be a class (implicitly, explicitly, or both).
>Of course, to make a coherent picture with extensions of rdfs:Class, we need
>to say that rdfs:subClassOf is transitive, etc.  But I think the rules above
>make a solid foundation for newcomers.

Yes, you are absolutely correct. I forgot about empty classes. Sorry 
if my email was misleading.

IHMC					(850)434 8903   home
40 South Alcaniz St.			(850)202 4416   office
Pensacola,  FL 32501			(850)202 4440   fax
Received on Monday, 26 August 2002 13:32:52 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 21:15:18 UTC