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Re: RDF-ISSUE-79 (undefined-datatype): What is the value of a literal whose datatype IRI is not a datatype? [RDF Concepts]

From: Richard Cyganiak <richard@cyganiak.de>
Date: Wed, 16 Nov 2011 21:13:23 +0000
Cc: public-rdf-wg@w3.org
Message-Id: <64DE4482-E349-4D16-B701-5347B8E1FCF8@cyganiak.de>
To: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Hi Antoine,

On 15 Nov 2011, at 21:23, Antoine Zimmermann wrote:
>> 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."

That just requires that *d* (the datatype) is in the datatype map, not that *u* (the IRI) is in the datatype map. If I have <u> owl:sameAs <v>, then it follows that IS(u)=IS(v). If (v,d) is in the datatype map, then it follows that IS(v)=d, which gives us IS(u)=d without u being in the datatype map.

That's how I read it anyways.

> 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

If my reasoning above is correct, then it doesn't require that <bar> is in the datatype map. It requires that <bar> denotes d, and that d is in the datatype map.

> Otherwise it is not in LV 

(That's actually not a requirement that I can find anywhere in RDF Semantics. RDF Semantics says that, if a literal's datatype IRI doesn't denote a datatype, then the literal “is treated as before”, it denotes “some unknown thing”. In other words, its denotation is entirely unconstrained, and interpretations that map the literal to a member of LV are fine. So the wording you quote looks a bit like a bug in OWL2 to me.)

> I'm just saying that the word "value" may be misunderstood. For instance, I would not consider a person to be a value.

I don't think there's any basis for that. There's nothing *formally* wrong with defining a datatype whose lexical space is social security numbers, whose value space is citizens, and whose L2V mapping involves the social security database.

Best,
Richard
Received on Wednesday, 16 November 2011 21:14:05 GMT

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