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Re: Proposal for ISSUE-12 language-tagged literals

From: Pat Hayes <phayes@ihmc.us>
Date: Sat, 16 Jul 2011 21:43:14 -0500
Cc: public-rdf-wg@w3.org
Message-Id: <BCC479C6-D971-48E4-8595-D79BA04A20CD@ihmc.us>
To: Andy Seaborne <andy.seaborne@epimorphics.com>

On Jul 16, 2011, at 10:52 AM, Andy Seaborne wrote:

> +1
> but I have a suggestion as well as to how to make rdf:LangString a datatype.
> 
> I'd rather make DATATYPE("foo"@en) be honest and say that it returns datatype rdf:LangString.
> 
> If we don't want to go down the route of modifying the L2V(d) mapping to work on that "foo"@en form (Pat's 'move the quotes out one level') then we could use the machinery in the parser process where is is currently.
> 
> Define the lexical space of rdf:LangString to be the empty set.  That makes it impossible to write a valid rdf:LangString in ^^ form.  Maybe someday, some future WG will change this but it will leave current RDF valid.
> 
> The value space is still <Unicode string, language tag>.

BUt if the lexical space is empty, then the only (mathematically) possible L2V mapping is the empty mapping, so this value space is irrelevant. None of it can be denoted by any literal, if we follow the current datatyping specs. 

Pat

> 
> Syntax "foo"@en has it's own mapping from syntax to value.  There's no reason why a Turtle parser does not have a rule, for Turtle and related syntaxes, that @ is treated in this way.  In RDF/XM, it is the xml:lang causing a similar translation from XML syntax.
> 
> Turtle parsers already have specific machinery for other datatype.  e.g. 123 for "123"^^xsd:integer .
> 
> 	Andy
> 
> On 13/07/11 15:51, Richard Cyganiak wrote:
>> 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
>> - 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.
>> 
>> 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.
>> 
>> The RDF Schema document is updated to add rdf:LangString and rdf:Text. No other changes to RDF Schema.
>> 
>> The SPARQL WG is asked to *consider* whether DATATYPE("foo"@en) should return rdf:LangString instead of error.
>> 
>> 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.
>> 
>> - 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.
>> 
>> ]]
> 
> 

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Received on Sunday, 17 July 2011 02:43:52 GMT

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