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Re: Comment on Last Call Working Draft of RDF Semantics document concerning untyped literals

From: pat hayes <phayes@ai.uwf.edu>
Date: Sun, 26 Jan 2003 09:52:36 -0700
Message-Id: <p05111b12ba59c1c2f7db@[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

>I believe that untyped literals do not work correctly in the RDF model
>theory. The semantic constraint on rdfs:Literal is, from Section 3.3
>
>    ICEXT(I(rdfs:Literal)) is a subset of LV
>
>However, the denotations of untyped literals are only required to be
>in LV.   Therefore the denotation of "a" is not necessarily in
>ICEXT(I(rdfs:Literal)).



>This situation has observable consequences.  For example
>        ex:foo ex:rel "a" .
>does not RDFS-entail
>        ex:foo ex:rel _:x .
>        _:x rdf:type rdfs:Literal .
>
>The situation is made even stranger in datatyped interpretations.  If
>there is a datatype whose value spaces includes the string "a", then
>entailment over this datatype has the above entailment.
>

That is true. This was a deliberate decision, but it could be 
changed. The essential change is to require that 
ICEXT(I(rdfs:Literal)) = LV, rather than being a subset of LV. In 
this case it would probably be better to also make LV part of the 
interpretation and add semantic conditions on it.

Unless anyone objects, I will make this change in the final 
publication version. The effect of this can be summarized by saying 
that untyped literals will then be treated like typed literals with a 
'blank' datatype which has the identity mapping as its 
lexical-to-value mapping.

Pat






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Received on Sunday, 26 January 2003 11:51:24 GMT

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