Overall it is unclear how signatures are to be support with queries where the intent is to automate gathering and responding data rather than having human involvement.  The descriptions allow for absence of a signature (in the absence of an agreement or an agreement that does not require that), but if the query is direct it seems that this would unduly burden the data source/responder to have the response signed by a person as Section 4.0.3 seems to imply.  In a task based approach, where a human being is participating in the flow already (not an automated task based approach), this could fit in the workflow where a user reviews and signs.  Suggest that the descriptions clarify more clearly who's signature is actually expected at the system level of an organization that actually has value and meaning considering that that person would not review every response manually.