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Re: RDF semantics: problems with entailment rules rdfs5 and rdfs9

From: <herman.ter.horst@philips.com>
Date: Thu, 13 Nov 2003 17:20:45 +0100
To: pat hayes <phayes@ihmc.us>
Cc: www-rdf-comments@w3.org
Message-ID: <OF38F049F7.0076E209-ONC1256DDC.002AB1FC-C1256DDD.0059DAA4@diamond.philips.com>

This uniformization operation on the entailment rules
tables is a useful change.

It seems that in rule rdfs7 it should be uuu instead
of xxx (and xxx instead of yyy).

And it would seem to become even more uniform if in rules
rdfs4a and rdfs9 yyy becomes xxx and in rule rdfs11
zzz becomes xxx (when the first option is chosen in
each case, as you do almost always).

Herman

-----------------------------------------------------------
>Two rdfs entailment rules do not seem to be stated
>in sufficient generality.
>This is indicated by the following two counterexamples
>to the rdfs entailment lemma.
>
>Example: graph G consists of triples
>   x subPropertyOf y
>   y subPropertyOf z
>where x y and z are blank nodes.
>In this case the semantics shows that
>G rdfs-entails the triple
>   x subPropertyOf z
>However this triple is not derived by rule rdfs5,
>since this rule requires x y and z to be URIs.
>
>
>A similar problem occurs with rule rdfs9.
>
>Example: graph H consists of triples
>   x subClassOf y
>   z type x
>where z is a blank node.
>According to the semantics, H rdfs-entails the
>triple
>   z type y
>This triple is however not derived by rule rdfs9
>since this rule requires z to be a URI.
>
>
>Herman ter Horst

Further to the above, I have amplified the textual explanation of the 
conventions, and gone through section 7 to bring the conventions in 
line in all the rule tables, so that the use of uuu, xxx, etc. is 
uniform throughout and corresponds exactly and unambiguously to the 
minimal syntactic needed to state the rules.

This was the original intention, but details got buried in multiple edits.

BTW this has the amusing consequence that 'www' is now used as a 
schematic for any subject, which has a kind of poetic justice to it.

Pat
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Received on Thursday, 13 November 2003 11:22:54 GMT

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