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rdfs:subClassOf and metaclasses

From: Piotr Kaminski <piotr@ideanest.com>
Date: Sun, 30 Jun 2002 20:11:04 -0700
To: www-rdf-comments@w3.org
Message-id: <010b01c220ac$f49c1a50$ada15018@transfinity>

Hi,

In short:

Do the subject and object of an rdfs:subClassOf statement have to both be
instances of the same (meta)class?

In long:

Are the following RDF triples valid (modulo syntax errors):

MA rdf:type rdfs:Class
MA rdfs:subClassOf rdfs:Class
MB rdf:type rdfs:Class
MB rdfs:subClassOf rdfs:Class
A rdf:type MA
B rdf:type MB
A rdfs:subClassOf B

The only thing I can find is in the RDFS spec is section 2.3.2, which says
that "Only instances of rdfs:Class can have the rdfs:subClassOf property and
the property value is always of rdf:type rdfs:Class".  The statements above
seem to satisfy this constraint.

The only related RDFCore WG issue I can find is rdfs-clarify-subClass-and
instance.

Incidentally, does anyone know how UML deals with this?  If, say, I have an
Actor and a Class (both subtypes of Classifier), can one extend the other?
A quick look at the UML 1.4 spec (sections 2.5.4.3 and 2.5.4.4 seemed the
most likely candidates) didn't produce enlightment.

        -- P.

--
  Piotr Kaminski <piotr@ideanest.com> http://www.ideanest.com
  It's the heart afraid of breaking that never learns to dance
Received on Sunday, 30 June 2002 23:11:11 GMT

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