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Re: Proposal for ISSUE-12 language-tagged literals

From: Antoine Zimmermann <antoine.zimmermann@insa-lyon.fr>
Date: Sun, 17 Jul 2011 10:47:35 +0200
Message-ID: <4E22A1A7.1060206@insa-lyon.fr>
To: public-rdf-wg@w3.org
Le 14/07/2011 15:08, Richard Cyganiak a écrit :
> On 14 Jul 2011, at 08:36, Antoine Zimmermann wrote:
>> In your proposal, rdf:Text is equivalent to rdf:PlainLiteral so it
>> seems redundent.
>
> No. rdf:Text is a class, rdf:PlainLiteral is a datatype.

But a rdfs:Datatype is also a rdfs:Class, and rdf:Text would be
owl:equivalentClass of rdf:PlainLiteral (according to the OWL semantics).

> Using rdf:PlainLiteral with rdfs:range creates expectations that its
> impractical lexical form is used.

I'd like to see examples of usage to be convinced, but at least
the spec of rdf:PlainLiteral clearly says that it is forbidden to use 
its lexical form, so normally it should never happen.

> "Plain literals without language tag" are now simply xsd:strings.
> "Plain literals with language tag" are not actually plain. So the
> name "plain literal" doesn't make sense any more.
>
> For these reasons, rdf:PlainLiteral is inadequate for use in
> rdfs:range statements.

Weird conclusion. Using rdf:PlainLiteral in a range statement exactly 
has the same effect as using rdf:Text. rdf:PlainLiteral is a 
recommendation, you can't just ignore it and remake a new almost 
equivalent proposal just because the name is inadequate. Moreover, i 
repeat that rdf:PlainLiteral was intended to be named rdf:text, but this 
name was rejected.


> Best, Richard

AZ.

>
>
>
>> Moreover, rdf:PlainLiteral was originally called rdf:text (see
>> http://www.w3.org/TR/2009/WD-rdf-text-20090421/ for instance) but
>> this name was rejected because the concept of "text" includes many
>> other features like directionality, font, structure, etc. I suggest
>> some changes below:
>>
>> Le 13/07/2011 16:51, Richard Cyganiak a écrit :
>>> We have addressed one half of ISSUE-12, the half about string
>>> literals *without* language tags.
>>>
>>> Here's a proposal for the other half, string literals *with*
>>> language tags and rdf:PlainLiteral. This is a very minimalist
>>> proposal.
>>>
>>> Summary: - add classes rdf:LangString and rdf:Text so we can
>>> better specify string literals as rdfs:range of properties
>>
>> don't add rdf:Text.
>>
>>> - add the technical term “language-tagged string” as an
>>> alternative to the current “plain literal with language tag” -
>>> ask OWL and RIF WGs to update rdf:PlainLiteral document to
>>> reflect the RDF WG decisions
>>>
>>> (This completes my ACTION-62.)
>>>
>>> Best, Richard
>>>
>>>
>>> [[
>>>
>>> A literal is either a typed literal or a language-tagged string.
>>>
>>> A language-tagged string is an<Unicode string, language tag>
>>> pair.
>>>
>>> "Plain literal with language tag" (from RDF 2004) is an
>>> alternative term for "language-tagged string". They are the same
>>> thing.
>>>
>>> rdf:LangString is the class of all language-tagged strings. It
>>> can be used in rdfs:range statements.
>>>
>>> rdf:Text is the class of all language-tagged strings and all
>>> Unicode strings. It can be used in rdfs:range statements.
>>
>> remove this line.
>>
>>> The RDF Concepts document is updated with the definitions above.
>>> No other changes to RDF Concepts.
>>>
>>> The RDF Semantics document is updated to make rdf:LangString and
>>> rdf:Text work. No other changes to RDF Semantics.
>>
>> remove "and rdf:Text"
>>
>>> The RDF Schema document is updated to add rdf:LangString and
>>> rdf:Text. No other changes to RDF Schema.
>>
>> remove "and rdf:Text"
>>
>>> The SPARQL WG is asked to *consider* whether DATATYPE("foo"@en)
>>> should return rdf:LangString instead of error.
>>
>> if rdf:LangString is not a datatype, then I think SPARQL should'nt
>> return it. Does SPARQL return rdfs:Literal?
>>
>>> The OWL and RIF WGs are asked to make changes to the
>>> rdf:PlainLiteral specification:
>>>
>>> - Clarify that the purpose of the document is *solely* to
>>> provide compatibility between RDF and specifications whose
>>> literal design does not support language tags.
>>
>> It is not the only purpose of rdf:PlainLiteral. The essential
>> purpose, AFAIK, is to allow systems to type all literals. It also
>> makes possible the definition of complex datatypes (for instance,
>> it is possible to define a datatype equivalent to your
>> rdf:LangString, or to the English-tagged strings, etc). Without a
>> proper datatype for that, such definitions are not possible.
>>
>>> - The spec should be changed to *only* cover strings *with*
>>> language tags, because strings without language tags now always
>>> have a datatype (xsd:string) and therefore don't need to be
>>> covered in this spec.
>>>
>>> - Instead of defining its complete own datatype
>>> rdf:PlainLiteral, the spec should only extend the rdf:LangString
>>> class so that it can serve as a datatype.
>>>
>>> ]]
>>
>>
>> -- Antoine Zimmermann Researcher at: Laboratoire d'InfoRmatique en
>> Image et Systèmes d'information Database Group 7 Avenue Jean
>> Capelle 69621 Villeurbanne Cedex France Tel: +33(0)4 72 43 61 74 -
>> Fax: +33(0)4 72 43 87 13 Lecturer at: Institut National des
>> Sciences Appliquées de Lyon 20 Avenue Albert Einstein 69621
>> Villeurbanne Cedex France antoine.zimmermann@insa-lyon.fr
>> http://zimmer.aprilfoolsreview.com/
>>
>
>


-- 
Antoine Zimmermann
Researcher at:
Laboratoire d'InfoRmatique en Image et Systèmes d'information
Database Group
7 Avenue Jean Capelle
69621 Villeurbanne Cedex
France
Tel: +33(0)4 72 43 61 74 - Fax: +33(0)4 72 43 87 13
Lecturer at:
Institut National des Sciences Appliquées de Lyon
20 Avenue Albert Einstein
69621 Villeurbanne Cedex
France
antoine.zimmermann@insa-lyon.fr
http://zimmer.aprilfoolsreview.com/
Received on Sunday, 17 July 2011 08:48:02 GMT

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