Revised resolution - change the valueset-trusted-expansion text to: If the designated "authoritative source" (as specified in the valueset-authoritativeSource extension, if present) is unable to provide a valid expansion, this extension indicates the base URL of a FHIR server that is an alternate trusted source where the value set expansion may be obtained.  This may be via a ValueSet $expand operation request (if supported by the server), or via the ValueSet endpoint directly which will return an instance of the ValueSet resource containing a persisted expansion (and the parameters that expansion is based on). This extension should only be used if the "authoritative source" (valueset-authoritativeSource extension) does not have a FHIR service which is capable of generating or returning a valid FHIR value set expansion.