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