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Re: skos:prefLabel without language tag

From: Bernard Vatant <bernard.vatant@mondeca.com>
Date: Fri, 24 Jun 2011 11:11:42 +0200
Message-ID: <BANLkTikX1iPr_4azbGQh6S3Y3c0gjRTB4w@mail.gmail.com>
To: Antoine Isaac <aisaac@few.vu.nl>
Cc: public-esw-thes@w3.org
Hello all

Thinking further about it, beyond the formal issue we have the question of
the expected behaviour of applications when meeting labels w/o language

In multilingual environments, the language tag is typically used to present
the concept to end users in their "user language". The unicity of the
prefLabel in the user language avoids clashes in the interface. Note that
some systems (e.g., Eurovoc and other OPOCE vocabularies) even require that
all concepts have a prefLabel in all supported user languages (e.g., EU
official languages), including default value rules (such as take the English
label if no label is available in Slovenian or Swedish).

In our (Mondeca ITM) system, a label (aka "name") has also a mandatory and
unique language tag, but one possible value is "no language". The behaviour
of the system regarding this tag is that such names are displayed whatever
the user language choice. Of course if one wants unicity of the displayed
name, it implies that if there is a "no language" name, there is no (other)
name tagged with a language.

Translated in SKOS, this rule would look like :

*If a Concept has a prefLabel value with no language tag, it cannot have a
different prefLabel value with a language tag.*

IOW the following is not conformant
ex:foo  skos:prefLabel 'A'; prefLabel 'B'@en

The following is conformant but somehow redundant
ex:foo  skos:prefLabel 'A'; prefLabel 'A'@en


2011/6/23 Antoine Isaac <aisaac@few.vu.nl>

> On 6/23/11 8:40 PM, Alan Ruttenberg wrote:
>> On Thu, Jun 23, 2011 at 1:52 PM, Houghton,Andrew<houghtoa@oclc.**org<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<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<http://www.w3.org/TR/rdf-plain-literal/#The_Comparison_of_rdf:PlainLiteral_Data_Values>

Bernard Vatant
Senior Consultant
Vocabulary & Data Integration
Tel:       +33 (0) 971 488 459
Mail:     bernard.vatant@mondeca.com
3, cité Nollez 75018 Paris France
Web:    http://www.mondeca.com
Blog:    http://mondeca.wordpress.com
Received on Friday, 24 June 2011 09:12:10 UTC

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