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OWL CR feedback: owl:Class 'vs' rdfs:Class causing pain. Is owl:Class really needed?

From: Dan Brickley <danbri@w3.org>
Date: Wed, 17 Sep 2003 20:38:47 -0400
To: public-webont-comments@w3.org
Cc: www-rdf-comments@w3.org
Message-ID: <20030918003847.GL17142@w3.org>

Hi

(Sent with my implementor hat on, rather than as W3C Team / RDF Core
person etc...)

A quick note to report on difficulties the existence of owl:Class is
causing in the FOAF world. FOAF is an RDF (RDFS/OWL) vocabulary,
(detailed at http://xmlns.com/foaf/0.1/) that is getting an encouraging
amount of usage on the public Web. FOAF files describe people,
documents, organisations, images etc. and their inter-relationships. I
have recently started making more extensive use of OWL within FOAF, 
to indicate inverse-property relations, inverse functional properties,
mutual disjointness between classes and suchlike. It works quite nicely
for this, and has helped us in our work and in explaining it. Thanks!

In promoting OWL via FOAF, I've repeatedly run into concerns and 
confusion w.r.t. the existence of the owl:Class class, since RDF 
(in RDF Schema) already provides a very similar concept, rdfs:Class.
This situation is causing problems, and I'm at a loss as to what to say 
to implementors (eg. [1]) except "I wish the OWL group would explain 
what to do, 'cos I don't know".

Are all RDF classes OWL classes? and vice-versa? Can this be expressed 
with (rdfs):subClassOf? It seems OWL is happy with using rdfs:subClassOf
(whose range and domain are rdfs:Class, at least in RDF/S)... does this 
mean that each FOAF class I define is also an owl:Class? Would it be 
good practice, appropriate, true etc for me to assert this within the 
FOAF namespace document?

Recently we have been exploring the use of OWL's fancier features, to 
say things like "Any Person whose foaf:workplaceHomepage is 
http://www.ilrt.bris.ac/uk is an ILRTStaffPerson". This is used in the 
FOAF Group mechanism, see http://xmlns.com/foaf/0.1/#term_Group
...in this part of the spec I copied the markup from OWL specs, and 
hence have used owl:Class instead of rdfs:Class. I find I have no 
sense of whether this is broken, invalid etc. usage or simply confusing.

If it is within the OWL WG's power to do anything to simplify the 
situation I would be hugely grateful...

Dan




[1] http://rdfweb.org/pipermail/rdfweb-dev/2003-September/011935.html



[1] http://rdfweb.org/pipermail/rdfweb-dev/2003-September/011935.html
Received on Wednesday, 17 September 2003 20:38:47 GMT

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