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Re: Rethinking ISSUE-12 with lang datatypes

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Fri, 27 May 2011 11:18:25 +0100
Message-ID: <4DDF7A71.7090907@epimorphics.com>
To: public-rdf-wg@w3.org


On 27/05/11 10:49, Ivan Herman wrote:
>
> On May 27, 2011, at 11:23 , Andy Seaborne wrote:
>
>>
>>
>> On 25/05/11 17:50, Antoine Zimmermann wrote:
>>> All,
>>>
>>>
>>> [disclaimer: I am not vehemently in favour of that proposal, just expressing my thoughts aloud.]
>>
>> In the same spirit: just thinking aloud.
>
> Ditto
>
>>
>> One of the limitations of datatypes is that lexical space is a 1D, the set of sequences of characters.  If we generalise datatypes for RDF to a "representation space" which can be multi-dimensional, we can formulate and relate language tagged datatypes quite simply.
>>
>> Restricting the representation space to 1D space of strings, we get back to lexical space and compatibility with XSD etc.
>>
>> rdf:String is a datatype where the rep space is
>>     (unicode strings) union (unicode strings, validLangTags)
>> The value space is<string>  union<string,validLangTags>
>>
>> rdf:LangTaggedString is a derived datatype of rdf:String, restricting the  represenation space to (unicode strings, validLangTags).
>>
>> rdf:lang{langTag} is a derived datatype of rdf:LangTaggedString, restricting the representation space to (unicode strings, {langTag})
>
> But, I believe, the alternative idea was slightly different. If we remove rdf:LangTaggedString from the equation altogether, and we keep only the rdf:lang-{langtag} as a series of datatypes, then the representation space is simply unicode strings plus a specific datatype. Ie, just like we have

Yes - but can we make rdf:LangTaggedString a datatype?

Without rdf:LangTaggedString as a datatype, there is no variability in 
the second position of the representation and it's 1D.

>
> "1"^^xsd:integer
> "1"^^xsd:double

"1"^^xsd:integer sameValueAs "1"^^xsd:double

> that are (afaik) disjoint as different, we would have
>
> "a"^^rdf:lang-en
> "a"^^xsd:string
>
> different.
>
> "a" is a shortcut for "a"^^xsd:string
> "a"@en is a shortcut for "a"^^rdf:lang-en
 >
> there is a question whether we would define rdf:lang-en as a subtype (subclass) of xsd:string; and it seems to be safer not to do that.

If it's a subtype, not just a subclass, then a lexical form has to map 
to the same value.

But "a"^^xsd:string is not sameValueAs "a"^^rdf:lang-en

	Andy

> SPARQL str()
>
> returns the unicode string and drops the datatype for all combination.
>
> Ivan

>
>>
>> "foo"@en is special syntax ("foo", "en").
>> (c.f. 123 for "123"^^xsd:string)
>>
>> SPARQL str() is defined to return the first element of a tuple.
>>
>> Then rdf:PlainLiteral is datatype with a 1D lexical space, encoding using "@" as a separator.
>>
>> (Does it say anywhere in RDF that derived datatypes must be subclasses?)
>>
>> 	Andy
>>
>
>
> ----
> Ivan Herman, W3C Semantic Web Activity Lead
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Received on Friday, 27 May 2011 10:18:56 GMT

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