DataService.endpointURL expands as an RDF literal, not an IRI

[SimonStier]

Bug Report

Describe the Bug

Type: normative

DataService.endpointURL is a string in the JSON Schema and is mapped without IRI coercion in the JSON-LD context, so it expands to an RDF literal.

Expected Behavior

dcat:endpointURL expands to an IRI. DCAT 3 defines it as the web-resolvable IRI of the service, and DCAT-AP 3.0.1 gives it range Resource, "the root location or primary endpoint of the service (an IRI)".

Observed Behavior

It expands to a literal, so a DSP catalogue cannot satisfy DCAT or DCAT-AP on that property.

artifacts/src/main/resources/catalog/dataset-schema.json:

"endpointURL": { "type": "string" }

artifacts/src/main/resources/context/dspace.jsonld:

"endpointURL": "dcat:endpointURL"

There is no implementer workaround: an @id object violates the schema, and the term is @protected.

Possible Implementation

"endpointURL": { "@id": "dcat:endpointURL", "@type": "@id" }

The serialized JSON is unchanged, only its RDF interpretation.

Same class as #277, where the schema and the context disagree about a property. #250 covers the lexical form of this property; a conforming implementation needs both.