It would be very useful if a variable in a Questionnaire could be populated via an x-fhir-query to an Operation. This would allow the operation's output Parameters to be put into a variable, and then FHIRPath could be used to pull out data from it and populate other fields or answer lists. For (currently brief) discussion on this see https://chat.fhir.org/#narrow/stream/179255-questionnaire/topic/x-fhir-query.20to.20operation.3F).