rdf:langString support in LinkML types

[mahdanoura]

In the W3C Web of Things standard, we are trying to utilise the LinkML model to describe the Thing Description standard [https://www.w3.org/TR/wot-thing-description11/]. The Thing Description document is structured as a JSON-LD document, where we need to use rdf:langString or the equivalent rdf:PlainLiteral Datatype for some of our attributes. Below, you can find the LinkML snippet I use for modelling the entity title, which can be either a string or a langString (e.g., "hue lamp"@en).

types:
  MultiLanguage:
    name: MultiLanguage
    description: Title with a language tag.
    from_schema: rdf
    exact_mappings:
    - rdf:PlainLiteral
    base: rdf:langString
    uri: rdf:langString
  title:
    description: >-
      Provides a human-readable title (e.g., display a text for UI representation) based on a default language.
    exactly_one_of:
      - range: string
      - range: MultiLanguage
    required: true
    slot_uri: td:title

However, the JSON Schema that is generated from this is:

"title": {
            "description": "Provides a human-readable title (e.g., display a text for UI representation) based on a default language.",
            "oneOf": [
                {
                    "type": "string"
                },
                {
                    "type": "string"
                }
            ],
            "type": "string"
        }

Any help would be appreciated. Thank you.

[kenwenzel]

@mahdanoura I'm also quite missing rdf:langString support in LinkML.
How do you want to represent the language-tagged literals in JSON? Are they simple strings or objects like {"label": "...", "lang": "en"}?

Furthermore, I think that base: rdf:langString is not correct as base expects a Python base type https://linkml.io/linkml-model/latest/docs/base/ (but maybe I'm just wrong). I guess it falls back to string in this case.

[cmungall]

This is a good proposal but the challenge is that linkml types are primitive, and it's often advantageous to model langStrings as objects, as in JSON-LD

See also a more general proposal https://github.com/orgs/linkml/discussions/2896