- From: Richard Cyganiak <richard@cyganiak.de>
- Date: Tue, 15 Nov 2011 16:15:01 +0000
- To: Antoine Zimmermann <antoine.zimmermann@emse.fr>
- Cc: public-rdf-wg@w3.org
Hi Antoine, On 14 Nov 2011, at 15:08, Antoine Zimmermann wrote: >> Is it somehow possible under RDFS-Entailment + D-Entailment to get a value for "foo"^^bar if bar is not in the datatype map? > > It is not possible. I think you're mistaken. if <bar> owl:sameAs <baz>, and <baz> is an IRI in the datatype map, then "foo"^^<bar> may have a well-defined value even if the IRI <bar> is not in the datatype map. On 14 Nov 2011, at 15:18, Antoine Zimmermann wrote: >> I note the following sentence: >> >> [[ >> The condition does not require that the URI reference in the typed literal be the same as the associated URI reference of thedatatype; this allows semantic extensions which can express identity conditions on URI references to draw appropriate conclusions. >> ]] > > I do not understand this phrasing. It speaks to the example above: The IRI in the typed literal may be <bar>, and the IRI in the datatype map may be <baz>, and we may know through an owl:sameAs statement that <bar> and <baz> denote the same datatype. In other words, the datatype denoted by <bar> might be in the range of the datatype map even though <bar> is not in the domain of the datatype (but <baz> is). >> So if the graph contains "xxx"^^<not-a-datatype>, then the literal might still acquire a value because<not-a-datatype> might be owl:sameAs xsd:string, but not in any of the standard RDF entailment regimes. > > In RDF or RDFS, it is not possible to say that something is not a datatype. Applications decide what are the datatypes in their local datatype map. A datatype map cannot be specified in RDF. Of course. The point was that <not-a-datatype> is an IRI that is not in the application's datatype map. >> So the formally correct thing to say would NOT be: >> >> “The value of a literal whose datatype IRI is not in the datatype map is unknown.” >> >> but: >> >> “The value of a literal whose datatype IRI does not denote a datatype in the datatype map is unknown.” > > Ok but "the value" seems to indicate that, although it is not know, it is a value in some kind of value space (an instance of rdfs:Literal). That just seems to be an unsound inference. A “value space” in RDF Concepts is a part of a “datatype”. We have just established that we are talking about literals “whose datatype IRI does not denote a datatype”. So there is no basis for inferring that the value of such a literal must be “in some kind of value space”. And regarding rdfs:Literal: From the statement “the value of X is unknown” you cannot reasonably infer the statement “the value of X is a member of rdfs:Literal”. I can see no basis whatsoever for that inference. Best, Richard
Received on Tuesday, 15 November 2011 16:15:41 UTC