GET /submodel-descriptors for getAllSubmodelDescriptors 404 is never a valid status code

[aaronzi]

What happens?

In the Submodel Registry, GET /submodel-descriptors does not return 404 Not Found. If no submodel descriptors are available, the endpoint returns 200 OK with an empty result instead.

Minimal example:

BASE_URL="http://localhost:8083"

curl -i \
  -X GET "$BASE_URL/submodel-descriptors"

Observed response:

• HTTP 200 OK
• Empty result array

The OpenAPI spec currently documents 404 for this operation.

Why is this wrong?

GET /submodel-descriptors represents a collection resource. An empty collection should be returned as 200 OK with an empty result, not as 404 Not Found.

This is also consistent with the AAS Registry, where GET /shell-descriptors returns an empty result when no descriptors exist.

Keeping 404 in the response set creates ambiguity for implementers, SDKs, and conformance tests.

How should it be fixed?

Remove 404 from the documented responses for GET /submodel-descriptors in the Submodel Registry OpenAPI spec.

Proposed response block:

paths:
  /submodel-descriptors:
    get:
      operationId: GetAllSubmodelDescriptors
      responses:
        '200':
          description: Requested submodel descriptors.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/GetSubmodelDescriptorsResult'
        '400':
          $ref: '#/components/responses/BadRequest'
        default:
          $ref: '#/components/responses/Error'

• I have signed the required Developer Certificate of Origin (DCO) already.

[sebbader-sap]

Decision from the AAS API TF (21.05.2026):
We will introduce the fix for this finding in the 3.1.3 bugfix and replicate it also into the V3.2 release. However, as this specific error case can anyway not happen for a V3.0 system, no additional V3.0 bugfix is needed.