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[LC Response] To Michael Smith (was Re: The definition of entailment in the Direct Semantics document)

From: Michael Smith <msmith@clarkparsia.com>
Date: Tue, 24 Feb 2009 09:10:38 -0500
To: W3C OWL Working Group <public-owl-wg@w3.org>
Message-Id: <1235484638.6819.4.camel@31-35-250.wireless.csail.mit.edu>
Dear Mike,

Thank you for your message
http://lists.w3.org/Archives/Public/public-owl-wg/2009Jan/0031.html on
the OWL 2 Web Ontology Language last call drafts.

The OWL Direct Model-Theoretic Semantics [1] defines entailment in
terms of interpretations and requires that all URIs in an ontology are
present in the vocabulary of any interpretation satisfying that
ontology. The OWL 2 Direct Semantics [2] document defines entailment
in terms of models, a change which relaxes the vocabulary constraint.
The change is intentional -- it is useful because it permits
tautologies to be entailed by the empty ontology and simplifies the
semantic specification.

The difference is demonstrated by the test case you have cited [3].
This test is a positive entailment under the OWL 2 Direct Semantics,
but was a negative entailment under the OWL Direct Model-Theoretic
Semantics used when the WebOnt WG approved the test case.

The definition of entailment in the OWL 2 Direct Semantics document
will not be changed in response to your comment.

Please acknowledge receipt of this email to <mailto:public-owl- 
wg@w3.org> (replying to this email should suffice). In your  
acknowledgment please let us know whether or not you are satisfied  
with the working group's response to your comment.
Mike Smith
on behalf of the W3C OWL Working Group

[1] http://www.w3.org/TR/owl-semantics/direct.html
[2] http://www.w3.org/2007/OWL/wiki/Direct_Semantics#Inference_Problems
[3] http://www.w3.org/2002/03owlt/Class/Manifest005#test
Received on Tuesday, 24 February 2009 14:11:51 UTC

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