- From: pat hayes <phayes@ihmc.us>
- Date: Tue, 16 Dec 2003 06:33:18 -0800
- To: Graham Klyne <gk@ninebynine.org>
- Cc: w3c-rdfcore-wg@w3.org
>Considering the RDF statement:
>
> ex:s ex:p "foo"^^ddd .
>
>where ddd is any URI other than rdf:XMLLiteral.
>
>Is this statement true, false or undefined in an RDF[S] interpretation?
>
>As far as I can tell, the denotation of "foo"^^ddd is defined by
>interpretation function IL, for which there are no semantic
>constraints in RDF and RDFS interpretations except for the datatype
>rdf:XMLLiteral.
>
>So I think the above statement is either True or False, depending on
>the interpretation used. So far, so good. But is this an
>RDFS-entailment:
>
> ex:s ex:p "foo"^^ddd .
>|=
> ex:s ex:p _:b .
> _:b rdf:type rdfs:Literal .
>
>Intuitively, I would have said "yes", but as far as I can tell from
>the semantics spec, the answer is "no". This is an entailment only
>in a {RDFS,ddd}-interpretation, because it is only a
>D-interpretation that places the required constraints on the
>relationships between I(rdfs:Literal), LV and IL.
>
>Am I correct?
Yes. Using a typed literal with an unknown type (which means any
except rdf:XMLLiteral in bare RDFS) is hostage to fortune. It denotes
*something*, but you only know its a literal value when you know that
the string is well-formed for that dtype: and if the dtype is
unknown, then you don't know that (yet).
Pat
>Is this what we expected?
>
>#g
>--
>
>PS: this would be consistent with the entailment rules, for which I
>was working through my implementation when I noticed this.
>
>
>------------
>Graham Klyne
>For email:
>http://www.ninebynine.org/#Contact
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Received on Tuesday, 16 December 2003 09:32:45 UTC