JSON-LD

JSON-LD (JSON Linked Data) is JSON with a @context: a list of contexts, named by URL, that define what each field and type means. Verifiable Credentials can be written in JSON-LD.

Why it matters for credentials

Credentials come in two formats:

For a JSON-LD credential, the signature is made over a normalized form of the credential. To make that form, the node expands every field using the contexts. A field or type that no context defines makes issuing or verifying fail.

Example: a HealthcareProviderRoleTypeCredential has the field roleCodeNL, which no JSON-LD context defines. Issuing it as ldp_vc fails; issuing it as jwt_vc works.

For new use cases, JWT credentials are simpler: no contexts to publish, agree on and configure.

Contexts in the Nuts node

A context URL is an identifier: a credential names it in @context, but it doesn't have to resolve. The Nuts node maps each URL to a copy it includes, so it never fetches these:

A use case with its own JSON-LD credential types publishes its own context. Every node in the use case must then be configured with it: either map the context URL to a local file, or allow the node to fetch it from that URL. See Custom credential configuration in the Nuts node documentation.