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Re: skos:prefLabel without language tag

From: Antoine Isaac <aisaac@few.vu.nl>
Date: Thu, 23 Jun 2011 22:46:28 +0200
Message-ID: <4E03A624.1020704@few.vu.nl>
To: public-esw-thes@w3.org
On 6/23/11 8:40 PM, Alan Ruttenberg wrote:
> On Thu, Jun 23, 2011 at 1:52 PM, Houghton,Andrew<houghtoa@oclc.org>  wrote:
>> Given these two situations:
>>
>>
>>
>> <skos:prefLabel>Dog</skos:prefLabel>
>>
>> <skos:prefLabel xml:lang=>Dog</skos:prefLabel>
>>
>> Does the inclusion of *both* prefLabel in a SKOS concept result in breaking
>> the rule S14 that no two prefLabel should have the same lexical value for
>> the same language tag?
>
> My read is that S14 is not applicable. In both cases the lexical value
> is the same - a plain literal without language tag. The RDFXML doesn't
> state that the language tag is "". It is syntax for the absence of a
> language tag. These two are different in the value space - without a
> language tag it is a string, with a language tag it is a pair of
> strings. The set of plain literals without language tags is *not* the
> set of pairs (string , "").
>
> Since the rule as stated applies to literals *with* language tags
> (they can't be the same unless they are there), S14 would not seem to
> be applicable.
>
> That said, this looks like a hole in the spec. It was probably the
> intention to also include the case that no two prefLabel without
> language tag have the same lexical value.
>
> -Alan


Yes, it certainly was.

I have to admit I don't know if there is a hole. It may seem reasonable that there exist some syntactic matching between literals having an empty tag and literals having no tag, as Simon reports.


> I think section 6.12 of the rdf syntax spec does result in the defaulting of language to at least "" in production 7.2.16- there doesn't seem to be another literal production that passes  the language feature.  I must admit that I am not certain how general this assumption is- there are other specs that seem to distinguish between <s> and <s,l>, but I think only  <s> \equiv <s,""> is consistent?
>
> Simon


However, this may be specific to one syntax.
The RDF abstract syntax and other specs are not mentioning that sort of things. Especially, the way the identity conditions are spelled out at [1,2] seem to argue against amalgamating absence of tag with presence of any tag (including an empty one).

Anyway, it could be that the simplest thing to do is to publish an erratum to clarify the original intent, rather than go into a discussion that is difficult, and would perhaps just be against a moving target, as RDF is currently being worked on... I'll forward the issue.

Cheers,

Antoine

[1]http://www.w3.org/TR/rdf-concepts/#section-Literal-Equality
[2] http://www.w3.org/TR/rdf-plain-literal/#The_Comparison_of_rdf:PlainLiteral_Data_Values
Received on Thursday, 23 June 2011 20:43:35 GMT

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