3.2.5.4.2 Executing a Received RetrieveValue Request
In addition to the directives specified in sections Common Rules: Receiving Responses from Data Service Requests (section 3.1.5.1), and Executing a Received Retrieve Request (section 3.2.5.4), the directives defined in this section apply when receiving a RetrieveValue request, see RetrieveValue Request (section 2.2.7.2.5).
If the value to be returned by a response to a RetrieveValue request is null, then the server MUST respond with a 404 (Not Found) and an error message formatted according to Error Response (section 2.2.8.1).