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Re: langstring, datatypes and semantics

From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Date: Thu, 23 Aug 2012 12:02:47 +0200
Message-ID: <5035FFC7.9070005@emse.fr>
To: public-rdf-wg@w3.org
Richard,


Thanks, I agree.


Le 22/08/2012 22:35, Richard Cyganiak a écrit :
> On 22 Aug 2012, at 10:30, Antoine Zimmermann wrote:
>> Langstrings are said to have a datatype IRI but no datatype is
>> defined for them.
>
> Correct.
>
>> Yet, the current spec refers to the "value space" of
>> rdf:langString. So, it leaves me wondering, is rdf:langString
>> denoting a datatype?
>
> No.
>
>> If not, what's a value space of something which is not a datatype.
>
> RDF Concepts does not say. It says that datatypes have a value space,
> and that a value space is associated with the IRI rdf:langString.

Fine, I can live with the formulation.


>
>> If yes, whatever datatype it denotes does not follow the definition
>> of datatype.
>>
>> Anyway, putting aside the phrasing of RDF Concepts, should the
>> following triple be axiomatic:
>>
>> rdf:langString  rdf:type  rdfs:Datatype .
>>
>> My opinion is no.
>
> I agree, it should not.
>
>> However, there should be:
>>
>> rdf:langString  rdf:type  rdfs:Class .
>
> This seems reasonable, given that we want to use rdf:langString in
> rdfs:range statements.
>
>> Another point is: can rdf:langString be used as a datatype IRI in
>> non-langstring literals?
>
> No.
>
>> The current draft of RDF Concepts does not dissallow it
>
> Wrong. The definition of literal is such that there can't be a
> literal with datatype IRI rdf:langString that is not a
> language-tagged string.

Ok, I misread the sentence, but I still have a problem with the 
definition of literals.

>
>> , so one can write:
>>
>> <s>  <p>  "abc"^^rdf:langString .
>>
>> I think this should be forbidden.
>
> It is forbidden. This has a datatype IRI of rdf:langString but no
> language tag, so it is not a literal as defined in the RDF abstract
> syntax.
>
>> So, it's not only that langStrings MUST have a datatype IRI equal
>> to rdf:langString, but also that any literal with this datatype IRI
>> MUST have a language tag.
>
> That's already the case, from the definition of literal and
> language-tagged string.
>
>> This would have a consequence on the definition of datatype maps.
>> If rdf:langString is not allowed for typed literals, then the
>> following line should be added to Section 5.4:
>>
>> "A datatype map MUST not contain the IRI rdf:langString, as it is
>> reserved for language-tagged strings and no formal datatype is
>> defined for this IRI."
>
> I don't see the benefit of saying that. If someone wants to define a
> formal datatype for rdf:langString, then why stop them? It would
> simply be a no-op, as there is no literal whose value would be
> defined by that datatype. Forbidding such a datatype might also
> create unnecessary roadblocks in the unlikely case that some future
> WG ever wants to update that rdf:PlainLiteral spec written by the RIF
> and OWL folks.

Ok, fair enough.


-AZ

>
> Best, Richard
>
>
>
>>
>>
>> Best, -- 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/
>>
>
>
>

-- 
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 Thursday, 23 August 2012 10:03:14 UTC

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