Multilingual support

[ddeboer]

Features

• For now, support only NL and EN.
• Offer terminology source metadata in both languages.
• Filter by language dynamically (instead of hardcoded NL, as it is now).

Overview of sources

Which sources support multiple languages?

• AAT: NL, EN, ES, FR, ZH
• Eurovoc: many languages
• RKD: NL, EN
• Uitvoeringsmedium: DE, EN, ES, FR, IT, NL
• Wikidata: many languages

All other sources are NL only, except Iconclass, which is EN only.

Tasks

• Extend the catalog with EN metadata.
• For the sources GraphQL endpoint, return both NL and EN; clients can then filter by language. Do we want name_nl, name_en or rather name as an object with language and value properties for more flexibility? Clients can then filter. Try to keep BC here.
• If the demonstrator’s language is EN, show catalog in EN.
• chore: Declare multiple dataset languages #1476
• On https://termennetwerk.netwerkdigitaalerfgoed.nl/sources, show the supported languages for each source.
• Parameterise the GraphQL terms query with a property languages which takes an array of preferred search/result languages: e.g. [nl], [nl, en].
• Return the language of each result in the terms query endpoint. Clients can then either show all results, hide non-preferred languages or optionally show them.

[ddeboer]

We could add prefLabels, altLabels, ... alongside prefLabel, altLabel, .... The new plurals would then contain a list of objects: [{language: 'en', value: 'Some literal value'}, {language ...}].

Do we like this approach?
Upside: full backwards compatibility.
Downside: looks less like SKOS, which uses singular prefLabel etc.

A remaining question is how in our SPARQL queries we can translate language-tagged literals to this object structure. Can we even access a literal’s language in SPARQL (other than filtering on it)?

[coret]

We could add prefLabels, altLabels, ... alongside prefLabel, altLabel, ....

This seem to be a solution outside of SKOS (purals not defined in https://www.w3.org/2009/08/skos-reference/skos.html)? It would be something like nde:PrefLabels and nde:altLabels?

[ddeboer]

Hence:

Downside: looks less like SKOS, which uses singular prefLabel etc.

We could prefix nde: but prefixes are not used in GraphQL APIs, so that would look weird to our API consumers.

[EnnoMeijers]

Could the SKOS-XL approach be helpful to model the GraphQL output? This seems to be relevant for multi lingual support, B&G uses SKOS-XL for GTAA source. If not, I am ok with the proposed approach, no need for prefixes indeed.