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Re: ACTION: task force unasserted triples

From: Jonathan Borden <jonathan@openhealth.org>
Date: Thu, 25 Apr 2002 11:00:43 -0400
Message-ID: <005101c1ec69$fb2f8040$0301a8c0@ne.client2.attbi.com>
To: <www-webont-wg@w3.org>, "Pat Hayes" <phayes@ai.uwf.edu>
now we're talkin' ***

Jonathan

*** to be understood as implying that as a member of the DTTF, I am leaning
heavily toward this proposal, reserving the right to change my mind at some
later date, perhaps tomorrow

----- Original Message -----
From: "Pat Hayes" <phayes@ai.uwf.edu>
To: <www-webont-wg@w3.org>
Sent: Wednesday, April 24, 2002 10:22 PM
Subject: RE: ACTION: task force unasserted triples


> A few more observations about the owl:Dark proposal
> (http://lists.w3.org/Archives/Public/www-webont-wg/2002Apr/0290.html).
>
> Given an RDF graph G, consider the subgraph containing all the
> triples in G that do not contain any uriref that occurs as the
> subject of a triple of the form
>
> aaa rdf:type owl:Dark .
>
> which is rdfs-entailed by G, ie which is in the rdfs-closure of G.
> Call this the 'light' subgraph of G, light(G).  Any RDF graph has a
> unique light subgraph which can be figured out by an RDFS reasoner.
>
> (This allows implicit 'darkening', eg by defining an rdfs:subClassOf
> owl:Dark and asserting something to be in the subclass, or by using
> rdfs:range. An alternative proposal would be to require the triple to
> occur in the graph explicitly. While syntactically simpler, that
> would complicate the relationship between RDFS and OWL since drawing
> a valid conclusion in RDFS could alter the 'darkness' of the
> vocabulary. )
>
> The desired semantic relationship between the languages can then be
> stated as the condition: Any satisfying OWL-interpretation of G is a
> satisfying rdfs-interpretation of light(G).
>
> Lemma: If S rdfs-entails G, then light(S) rdfs-entails light(G).
>
> This means that drawing valid RDFS conclusions from some OWL (even on
> the 'dark' vocabulary) isn't going to produce any unwanted
> conclusions. It might produce some conclusions that are dark, but it
> isn't going to produce any light ones that it shouldn't produce, ie
> that OWL would find embarrassing.
>
> More later, hopefully with some test cases.
>
> Pat
>
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>
Received on Wednesday, 24 April 2002 22:48:16 GMT

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