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Re: more problems with closures

From: pat hayes <phayes@ai.uwf.edu>
Date: Sun, 1 Jun 2003 19:59:12 -0500
Message-Id: <p0521061cbb004ed0609a@[10.0.100.24]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: www-rdf-comments@w3.org

>It occurs to me that all the closures are incomplete.
>
>For example,
>
>	ex:a ex:b ex:c .
>	ex:d ex:e ex:c .
>
>entails
>
>	ex:a ex:b _:x .
>	ex:d ex:e _:x .
>
>but that this cannot be derived in any of the closure rule sets.

Yes, you are right; these rules need to be stated as operations on 
subgraphs, following the wording of the instance lemma.  Or else the 
notion of 'new' needs to be re-defined, but that would be ugly. 
Sigh.  If only we actually had quantifiers in the syntax.  Maybe it 
was a mistake to try to keep these rules as simple as possible. I 
will fix this in the next day or so, not sure yet exactly in which 
way.

>
>This means that the characterisation of the instance lemma by rules se1 and
>se2 is incorrect.
>
>
>Also, as the canonical form of an XML document is some sort of string,

That is unfortunately a controversial claim. On some views of the 
matter, XML documents and strings are distinct classes.  Therefore, 
the MT deliberately allows the possibility that XML documents and the 
character strings of plain literals can be distinct, so the following 
entailment is not considered to be valid without some other 
antecedents. In a word: plain literals and XML literals might be 
disjoint sets in some interpretations.

I ought to put this into an explicit comment, however, for 
clarification.  Obviously, the whole XML literal stuff in the MT 
needs to be re-done: I am awaiting confirmation from Jeremy that I 
have it right.

Pat

>
>	ex:a ex:b "2"^^rdf:XMLLiteral
>
>entails
>
>	ex:a ex:b "...."
>
>where .... is the string that is the canonical form of "2".  This is not
>however implied by the RDF closure rules.
>
>peter


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Received on Sunday, 1 June 2003 20:59:12 GMT

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