With the support for ECL in definition of FHIR ValueSets it is possible to intensionally define (by filters and rules rather than listing codes explicitly) a ValueSet by

1. creating a reference set in a SNOMED CT (or extension) release and exposing an Implicit ValueSet based on the reference set
2. do not define a reference set and instead define the ValueSet directly using ECL (or other filters) as required

Both options have pros and cons. Option 1 for example provides a reference set in a SNOMED CT release which can be used by those consuming RF2 and not using FHIR whereas option 2 cannot. However option 2 provides some advantages as well, as the ValueSet definition can be reused and re-evaluated against other (perhaps downstream) SNOMED CT extensions, however option 1 doesn't provide a standard, well used way to expose the machine processable conditions defining the reference set content.

This page is intended to start a discussion and capture the groups thoughts on the pros and cons of both approaches and consider best practices when making this choice.

Invitation to contribute a list of Pros and Cons to this page.