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RE: Dark triples motivation

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Wed, 17 Apr 2002 13:07:35 +0100
To: "Jeremy Carroll" <jjc@hplb.hpl.hp.com>, <www-webont-wg@w3.org>
Message-ID: <JAEBJCLMIFLKLOJGMELDOELCCDAA.jjc@hplb.hpl.hp.com>
>
> I did my best at:
>
> http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2002Apr/0178.html
>


In light of the feedback, I have been clarifying my idea of what the problem
is.

Problem statement:

Layering on top of RDF involves using graph syntax to encode OWL concepts.
If such graph syntax is asserted then the RDF model theory assigns meaning
to such syntax specifically denoting things in the domain of discourse that
correspond to the syntactic expressions of OWL. Given this, an OWL model
theory with appropriate entailments (in which the theory of classes in OWL
is recognisable as a subtheory of some well known set theory) is difficult
and problematic to construct.


Solution statement:

Using unasserted triples for the syntactic structures of OWL allows an OWL
interpretation to assign a meaning to a subgraph which need bear no
correspondence with the meaning of corresponding asserted triples in RDF.



Example:

The RDF document:

<rdf:Description rdf:about="#John">
   <rdf:type rdf:resource="#Student">
   <rdf:type rdf:resource="#Employee">
</rdf:Description>

understood with rdf:type denoting set membership, would, under almost all
set theories, entail #John being a member of the intersection of #Student
and #Employee.
In daml+oil this is said:

<rdf:Description rdf:about="#John">
   <rdf:type>
    <daml:class>
      <daml:intersectionOf rdf:parseType="daml:collection">
         <daml:class rdf:ID="Employee"/>
         <daml:class rdf:ID="Student"/>
     <daml:intersectionOf>
    </daml:class>
   </rdf:type>
</rdf:Description>

If we leave the daml class expression:


<rdf:RDF>
    <daml:class>
      <daml:intersectionOf rdf:parseType="daml:collection">
         <daml:class rdf:ID="Employee"/>
         <daml:class rdf:ID="Student"/>
     <daml:intersectionOf>
    </daml:class>
</rdf:RDF>

as unasserted then OWL can assign a meaning to this expression wholly
independently of RDF.



Have I got it?

Jeremy
Received on Wednesday, 17 April 2002 08:09:19 GMT

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