DTR 2.1.0 (and up) requires the http://hl7.org/fhir/uv/sdc/STU3/StructureDefinition-sdc-questionnaire-questionnaireAdaptive.html extension to always have a valueUrl ; defined as "a URL for the base URL of a server that can perform the nextQuestion operation for this particular questionnaire." My question is about this scenario: The DTR client has called $questionnaire-package on a known payer DTR server endpoint The response includes an adaptive Questionnaire, with the required questionnaireAdaptive extension specifying a base URL Is the expectation, if the valueUrl is different, that the client use the extension value for subsequent $next-question calls, _not_ the endpoint it just called $questionnaire-package on?

The endpoint will always be the full URL. So if you invoke " http://someserver.org/$questionnaire-package ", the valueUrl would be " http://someserver.org/$next-question " if they are hosted on the same server. However, there's no expectation they will be on the same server, or even that all questionnaires returned in a single package will have the same server.

So it is expected that the client uses the valueUrl for $next-question ? So (and this is kind of the motivation for my question), if the client is calling a DTR server which is proxying to multiple other DTR servers, that proxy server would be expected to rewrite the valueUrl of questionnaireAdaptive before returning the QuestionnaireResponse to the calling client?

If the $next-question calls have to run through the proxy too, then yes. Though if its possible for the EHR to connect directly, that's presumably going to be more efficient.

Thanks. Agree re: efficiency, but may not be possible, alas.

If it's not clear from the spec that the provided URL is the one expected to be used, feel free to submit a change request asking for a clarification.

I may do that. Although actually, I think the real non-obvious thing is the requirement for the valueUrl to be the complete path to the $next-question operation, not the server's base URL as the extension definition strongly implies ("the base URL of a server that can perform the nextQuestion operation").

It looks like I was wrong in my example. I agree that baseUrl would be " http://someserver.org " and would not have $questionnaire-package there. However, it could be a different server than the $questionnaire-package URL