JSON-LD has already tackled the problem of mapping between tree structures and language-aware RDF. There are 3 idioms

JSON-LD Idioms

1 Language in Context

{
  "@context": {
    "title": "http://schema.org/name",
    "@language": "en"
  },
  "@id": "http://example.org/book1",
  "title": "War and Peace"
}

==>

<http://example.org/book1> <http://schema.org/name> "War and Peace"@en .

2 Language-tagged string objects

{
  "@context": {
    "title":  { "@id": "http://schema.org/name", "@container": "@language" }
  },
  "@id": "http://example.org/book1",
  "title": {
    "en": "War and Peace",
    "fr": "Guerre et Paix",
    "ru": "Война и мир"
  }
}

==>

<http://example.org/book1> <http://schema.org/name> "Guerre et Paix"@fr .
<http://example.org/book1> <http://schema.org/name> "War and Peace"@en .
<http://example.org/book1> <http://schema.org/name> "Война и мир"@ru .

3. Explicit value objects instance

{
  "@context": { "@vocab": "http://schema.org/" },
  "@id": "http://example.org/book3",
  "title_values": [
    { "@value": "Don Quixote", "@language": "en" },
    { "@value": "Don Quijote", "@language": "es" }
  ]
}

==>

<http://example.org/book3> <http://schema.org/title_values> "Don Quijote"@es .
<http://example.org/book3> <http://schema.org/title_values> "Don Quixote"@en .

Note there is no 4th idiom that allows you to write "hello@en:" and have it be treated as a language tag

Mapping to LinkML

3 Explicit value objects instance

Some schemas do have explicit value objects instances, e.g. reproNim

https://github.com/ReproNim/reproschema/blob/ac35394773e66e2aab8a3d26e4acce1fabb1ce63/linkml-schema/reproschema.yaml#L493-L497

https://github.com/ReproNim/reproschema/blob/ac35394773e66e2aab8a3d26e4acce1fabb1ce63/linkml-schema/reproschema.yaml#L187-L197

it uses the convention of using rdf:langString as the class_uri, which is a good one:

langString:
    description: RDF langString tuple
    slots:
    - langstring_prefix
    - langstring_value
    class_uri: rdf:langString

However, the linkml core does not know of this convention. Also we need a convention to map each of the slots to @language and @value

LinkML requirement:

• specify a convention for mapping tuple objects plus their slots to rdf:langString

2 Language-tagged string objects

Requirements are the same as for (3), use standard linkml mechanisms to map to dicts

1 Language in Context

Conceptually simple. However, there is no direct analog of @context.

Proposal

Provide a general purpose way to map LinkML slots to JSON-LD @tags, at schema time, and at run time.

classes:
  Book:
    title:
      range: MyLangString
  MyLangString:
    attibutes:
      my_lang:
         implements: [jsonld:language]
      my_val:
        implements: [jsonld:value]

For 1:

classes:
  Book:
    title:
      range: string
      annotations:
        jsonld.language: en

Consideration: any_of ranges

It's common in rdf docs (and JSON-LD serializations) for the value for the same property to be a mix of simple strings and langStrings. In this case standard any_of ranges can be introduced by the schema author.

Consideration: Dynamic injection

A variant of 1, where the interpretation of an atomic string is interpreted at runtime

# schema

classes:
  Container:
    attributes:
      language:
        implements: [jsonld:language]
      books:
  Book:
    attributes:
      id:
      title:
        range: string
        implements: [jsonld:language]

# data
language: en
books:
- id: book:123
  title: War and Peace

Consideration: Multilingual schemas

In LinkML, schemas are data that instantiate the linkml metamodel, so any solution that works for data should work for

alternative proposals considered

Mapping types to rdf:langString

https://github.com/orgs/linkml/discussions/2199

This is a good proposal but linkml types are primitive and for cases 2 and 3, the representation at the tree level has to be an object (unless we go with 4, which is not a json-ld idiom)