LC Responses/MS4

From http://lists.w3.org/Archives/Public/public-owl-wg/2009Feb/0165.html PeterPatel-Schneider 12:49, 20 February 2009 (UTC) Added boilerplate at end

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.


[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


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Regards,
Mike Smith
on behalf of the W3C OWL Working Group