This comment was entered by Michael Lawley while reviewing @FHIR-23785, which is part of a block vote. @FHIR-23785 was removed from the block vote. 

The resolution for 23785 (as of 6/18/2020) is to update the text description for the extension (valueset-trusted-expansion) to the following: 

If the designated "authoritative source" (as specified in the valueset-authoritativeSource extension, if present) is unable to provide a valid expansion, this extension indicates an alternate authoritative source where the value set expansion may be obtained.

This extension should only be used if the "authoritative source" (valueset-authoritativeSource extension) does not have a FHIR service which is capable of generating a valid FHIR expansion.

Michael's comment:

• this is currently a URI(dentifier), not URL(ocation) but the definition suggests that this is meant to be directly resolvable – suggest that the type be changed to URL
• definition should clarify what this actually refers to (so a tool knows how to use it). Specifically, is this the URL of an actual expansion (ie resolving the link will directly supply a ValueSet with an expansion), or is it intended to be the (base) FHIR endpoint and thus used to construct an $expand operation (or is it something else)?

Discussed at the FHIR tracker call on 6/18/2020. 

Discussion: a URL is a URI

Text as proposed in 23785 could be adjusted to address the concerns. 

This ticket must be addressed along with 23785 and any changes made at the same time.