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RE: rdfs:Class and rdfs:Resource

From: Jon Hanna <jon@spin.ie>
Date: Mon, 6 Jan 2003 16:20:32 -0000
To: <www-rdf-interest@w3.org>
Message-ID: <NDBBLCBLIMDOPKMOPHLHEEOHELAA.jon@spin.ie>

> I am a little confused about some aspects of RDFS. To start with, is it
> true that the following statements are equivalent?
>
> <Foo rdf:about="x"/>
> <rdf:Description rdf:about="x" rdf:type="Foo"/>

Close enough:

<rdf:Description rdf:about="x">
	<rdf:type rdf:resource="http://somenamespaceuriFoo"/>
</rdf:Description>

> If the above assumption holds, then what puzzles me is the consequence of
> the following extracts from the RDFS:
>
> 1.)
> <rdfs:Class rdf:about="http://www.w3.org/2000/01/rdf-schema#Resource">
> </rdfs:Class>
>
> 2.)
> <rdfs:Class rdf:about="http://www.w3.org/2000/01/rdf-schema#Class">
>    <rdfs:subClassOf
> rdf:resource="http://www.w3.org/2000/01/rdf-schema#Resource"/>
> </rdfs:Class>
>
> 1) states that rdfs:Resource is an instance of rdfs:Class. And 2) states
> that rdfs:Class is an instance of itself and a subclass of rdfs:Resource.
> Which means that rdfs:Class is a subclass of one of it's own
> instances. Am
> I correct here?

Yes. Breaking the above down:

A. rdfs:Resource is an instance of rdfs:Class.
B. rdfs:Class is an instance of rdfs:Class
C. rdfs:Class is a subClassOf rdfs:Resource.

A. Easily done. "Resource" is a concept of a type of thing. As such it is an
instance of rdfs:Class.

B. Easily done. "Class" is a type of thing. As such it is an instance of
rdfs:Class.

C. Easily done. If something is a class it is a resource, but the converse
doesn't hold. Hence "Class" is a subclass of "Resource".

Loops of this type are inevitable given the nature of the resources and
classes described in the RDFS Schema. It's to be expected in what is a
schema for schemata!

Loops like this are rarer in most other RDF, but they do occur.
Received on Monday, 6 January 2003 11:11:17 GMT

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