Will provide clarification on the expected response as follows: where the requested data was specified as a query request, the response will be a query response Bundle in all cases.  If no records were found, the Bundle will be empty and show a count of 0 resources - as would be the case if the query had been executed directly.  (Note that this may be different from the 'internal' results of the query as some of the results originally returned might have been manually or automatically filtered out prior to returning the response to the payer.) where the requested data was specified as one or more document codes, the solution will vary depending on whether we stick with Communication or move to using Task.  For Communication, we will use Communication.payload.contentCodeableConcept with a specific coded value indicating no records were found (and possibly text providing more explanation).  If we use Task, then the Task would be changed to a status of 'failed' and have a status reason indicating that no recordw were found, possibly with supporting text. In situations where the situation is not "no records found" but rather "I have data, I'm not giving you the data, and I want you to know that - because it may be possible to escalate or use a different process to access the data", the spec will indicate that that's to happen via an OperationOutcome within the empty search response Bundle for the query case and using an alternate standard code in the document codes case.