- From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
- Date: Tue, 15 Nov 2011 22:23:58 +0100
- To: Richard Cyganiak <richard@cyganiak.de>
- CC: public-rdf-wg@w3.org
Hi Richard, Le 15/11/2011 17:15, Richard Cyganiak a écrit : > 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. Assuming that owl:sameAs was in the RDF/RDFS spec, this even would not make "foo"^^<bar> be interpreted identically as "foo"^^<baz>. The interpretation of typed literals is not influenced by anything in the ontology, even in OWL. "foo"^^<bar> is always interpreted as L2V(D(<bar>))("foo") according to the datatype map D. FYI, look at section 4.2 of the OWL 2 RDF-based semantics: "IL is a mapping from typed literals "s"^^u in V to their denotations in IR, where IL("s"^^u) = L2V(d)(s), provided that d is a datatype of D, IS(u) = d, and s is in the lexical space LS(d); otherwise IL("s"^^u) is not in LV." So the interpretation of "s"^^u (or "foo"^^<bar>) is in the value space of <bar> if and only if <bar> is in the datatype map AND "foo" is in the lexical space of D(<bar>). Otherwise it is not in LV (or, I would say, it is not a "value"). > > 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. I'm just saying that the word "value" may be misunderstood. For instance, I would not consider a person to be a value. But "foo"^^<not-a-datatype> may denote a person or anything. > > Best, Richard -- Antoine Zimmermann ISCOD / LSTI - Institut Henri Fayol École Nationale Supérieure des Mines de Saint-Étienne 158 cours Fauriel 42023 Saint-Étienne Cedex 2 France Tél:+33(0)4 77 42 66 03 Fax:+33(0)4 77 42 66 66 http://zimmer.aprilfoolsreview.com/
Received on Tuesday, 15 November 2011 21:24:27 UTC