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Re: Comment on Last Call Working Draft of RDF Semantics document concerning RDFS closure rules

From: pat hayes <phayes@ai.uwf.edu>
Date: Sun, 26 Jan 2003 11:21:55 -0700
Message-Id: <p05111b19ba59d4622acd@[10.0.100.247]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: www-rdf-comments@w3.org, w3c-rdfcore-wg@w3.org

>The closure rules for RDFS are incomplete.  For example,
>    ex:foo ex:prop "a" .
>RDFS-entails
>    ex:foo ex:prop _:x .
>    _:x rdf:type rdfs:Resource .
>However, this does not come out of the RDFS closure rules.
>This means that the RDFS entailment lemma is false.

That is true, and I had indeed not previously noticed this case, 
which requires the notion of closure to be re-worded slightly. The 
inference can be obtained as follows:

ex:foo ex:prop "a" .
|=
ex:foo ex:prop _:x .

is sanctioned by the general RDF entailment conditions, and the other 
triple is then inferred by the rule rdfs4b. However, this means that 
the closure rules need to be applied *after* some RDF inference is 
performed.

The definition of closure will be re-worded so as to first add all 
existential conclusions on triples involving literals, then apply the 
closure rules. This will handle this exceptional case.

Pat




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Received on Sunday, 26 January 2003 13:35:58 EST

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