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RE: ACTION: task force unasserted triples

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Wed, 24 Apr 2002 13:46:21 -0500
Message-Id: <p05101534b8eca735219e@[65.217.30.94]>
To: www-webont-wg@w3.org
Cc: brian_mcbride@hp.com
Let me make a concrete proposal.

1. There is no change at all to RDF, and the RDF core WG is relieved 
of all requests to do anything about this matter.

2. Every OWL expression is a set of RDF triples.

3. OWL introduces a special class name owl:Dark (which can be an 
rdfs:Class). Any assertion of the form

AAA rdf:type owl:Dark .

where AAA is a uriref, is given a special interpretation by OWL as 
follows: it means that the RDF meaning of any triple containing AAA 
is not inherited by OWL. In other words, an OWL interpretation which 
satisfies the RDF graph is not required to make those triples true; 
other urirefs which occur in them (and nowhere else) are not required 
to denote; and they are not OWL-entailed by the RDF graph. While of 
course any such triple may have some other meaning imposed on it by 
the OWL semantics, any meaning imposed on it by the RDF model theory 
is ignored by OWL.

4. The following is true in all OWL interpretations:

owl:Dark rdf:type owl:Dark .

5.  Several other triples will also be true in all OWL 
interpretations, but we can decide those as we go along. For example, 
to handle DAML+OIL, we should add the triples:

daml:List rdf:type owl:Dark .
daml:first rdf:type owl:Dark .
daml:rest rdf:type owl:Dark .
daml:nil rdf:type owl:Dark .

In RDFS, owl:Dark is a class containing things that might be termed 
OWL-ghoulies; in OWL, it is a kind of syntactic marker which is used 
to decide which RDF triples need to be interpreted as having 
assertional import in OWL.

Including the appropriate list of triples (analogous to the DAML list 
in 5 above) could be a user option, or it could be considered to be 
done 'automatically', and this could even be reflected in two subtly 
different compliance levels for OWL .

I think that should be enough to handle everything.

Pat

PS. For Jos: dereferencing a URI is considered to automatically put 
all the urirefs you find in the document into owl:Dark.


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Received on Wednesday, 24 April 2002 14:46:23 GMT

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