RDF API: Ensure literal's have a (correct) language tag.

[svandenhoek]

Is your feature request related to a problem? Please describe. Best practice is to ensure String literal's define their language. Also FDP v1.2 defines this: https://specs.fairdatapoint.org/fdp-specs-v1.2.html#repositorymetadata

Name of the FAIR Data Point with the language tag.

EMX2 docs state language tags can be adjusted for labels here (not sure how this works in practice though, couldn't quickly find how to change), though a more robust system is probably needed if language should be defined per-column.

Describe the solution you'd like

• Column-specific language toggles.
• Columns with same semantics should be merged in RDF API (with a check that the language tag differs) so that they can be combined in the output:

  <subject> <predicate> "literal1"@en ,
                    "literal2"@de

Describe alternatives you've considered

1. Leave it as is.

Not really preferred as RDF standards might require language tag.

2. Simply add @en.

Possible short-term solution while only English is allowed, though this means if a user would add non-English text in the tables, the generated RDF is malformed.

Additional context Current example output:

<http://localhost:8080/my_FDP/api/rdf/Container?id=Example_FDP_catalog_container>
  a My_FDP:Container, qb:Observation, <http://www.w3.org/ns/ldp#DirectContainer>;
  dcterms:title "Example FAIR Data Point catalog container";

Preferred output:

<http://localhost:8080/my_FDP/api/rdf/Container?id=Example_FDP_catalog_container>
  a My_FDP:Container, qb:Observation, <http://www.w3.org/ns/ldp#DirectContainer>;
  rdfs:label "Example_FDP_catalog_container"@en;
  dcterms:title "Example FAIR Data Point catalog container"@en, "Voorbeeld FAIR Data Point catalog container"@nl;

[mswertz]

should we then default this to 'en'?

[svandenhoek]

For now hardcoded language tag or an advanced setting with default language tag seem like the best approach until we run into issues where we need multi-language support inside a single schema.