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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: Thu, 10 Nov 2011 17:43:49 +0000
Cc: Antoine Zimmermann <antoine.zimmermann@emse.fr>, public-rdf-wg@w3.org
Message-Id: <08EAAEDA-B4B7-4B48-AFF2-52D1F1FEF877@cyganiak.de>
To: Alex Hall <alexhall@revelytix.com>
Alex,

On 10 Nov 2011, at 16:33, Alex Hall wrote:
> That's almost exactly what RDF Semantics 2004 says: "Typed literals whose type is not in the datatype map of the interpretation are treated as before, i.e. as denoting some unknown thing." (Section 5.1)

Oh, I thought I carefully read all of Section 5 but had missed that sentence. That addresses the situation indeed.

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.
]]

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.

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.”

Oh well.

> I would prefer to have literals of type rdf:LangString denote themselves in all interpretations rather than some unknown thing, but I don't know how best to make it happen.  Clearly it can't be done through the L2V mechanism.

That's easy – a new row in the first table in Section 1.4:
http://www.w3.org/TR/rdf-mt/#gddenot

If E is a language-tagged string with lexical form aaa and language tag ttt in V then I(E) = <aaa,ttt>

and appropriate exceptions have to be stated in some places that talk about datatype IRIs – “if the datatype IRI is not rdf:langString, then …”

Best,
Richard
Received on Thursday, 10 November 2011 17:44:19 GMT

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