Re: ISSUE-137: Proposal to add sh:langShape

What Holger proposes is flexible and we have the option to reuse some
existing constructs but I  have some concerns about this design

the reason is that we currently have focus node constraints and property
(path) constraints
with this approach we create a new construct only for languages that is not
clear what it is and how it operates e.g.
 - if there are any differences in the meaning of e.g. sh:in when it is
used in a language context and when not
 - how sh:langShape inter-operates with the extension mechanism and
 - what does it mean to have e.g. sh:class in a sh:langShape (does all
constraints apply in all places?)

I would prefer the creation of a few new constraint components e.g.
sh:languageIn that allows us to enable (if we want) the RFCs Andy suggested.

Another option would be to generalize the mechanism Holger suggested and
provide transformation functions on the focus nodes / values a shapes
selects
This way we would be able to e.g. create a sets/lists of language tags,
unwrap RDF lists, etc and apply the shacl core components on the
transformed values
However, I think it is a bit late to try something in this direction

Best,
Dimitris

On Fri, Sep 9, 2016 at 2:58 AM, Holger Knublauch <holger@topquadrant.com>
wrote:

> I was given the task of writing up sh:langShape today. I already did a few
> months back:
>
> https://lists.w3.org/Archives/Public/public-data-shapes-wg/
> 2016Mar/0262.html
>
> From the list of requirements at
>
> https://www.w3.org/2014/data-shapes/wiki/Proposals#ISSUE-
> 137_Missing_constraint_for_language_tag
>
>
>    - In SKOS, there can be only one prefLabel per language tag
>
> Already exists: sh:uniqueLang true
>
>    - Constrain the valid language tags to a provided set, e.g. (@en, @de,
>    @fr)
>
> See my email, sh:langShape [ sh:in ( "en" "de" "fr" ) ]
>
>    - Require that all literals have/do not have a language tag
>
> Already exists: sh:datatype rdf:langString
>
>    - Require that a particular property have a set of literals, one each
>    language tag, e.g. "there must be 3 instances of dct:abstract; the values
>    must be literals; there must be one literal for each valid language code
>    (@en, @de, @fr)"
>
> Can be expressed through a combination of sh:minCount = 3, sh:maxCount =
> 3, sh:uniqueLang. (What are "instances of dct:abstract"?)
>
>    - Check that the language tag is 2-letter | 3-letter | does/does not
>    have hyphens
>
> sh:langShape [ sh:minLength 2 ; sh:maxLength 2 ; or: sh:pattern "... regex
> ..." ]
>
>    - Check that the 2 or 3-letter tag is valid
>
>
> Assuming that the list of valid tags is stored somewhere, e.g. in an
> rdf:List iso:ValidLanguages:
>
> sh:langShape [ sh:in iso:ValidLanguages ]
>
> I don't think maintaining such a list ourselves is within the scope of the
> WG, yet it could be expressed in the Core language.
>
>
> PROPOSAL: Add sh:langShape as outlined. Meaning: if a value node has a
> language tag then the string of the language tag itself needs to have the
> given sh:Shape.
>
>
> Holger
>
>


-- 
Dimitris Kontokostas
Department of Computer Science, University of Leipzig & DBpedia Association
Projects: http://dbpedia.org, http://rdfunit.aksw.org,
http://aligned-project.eu
Homepage: http://aksw.org/DimitrisKontokostas
Research Group: AKSW/KILT http://aksw.org/Groups/KILT