Given that the expansion of a value set is what is actually of use and an expansion is determined by the value set definition version plus the code system version used, the binding strength REQUIRED is unclear as to if a specification is dictating a STATIC unchanging expansion for use, or if one or both of the versions noted can change. Presumably a binding can specify a value set version if the value set canonical plus version is used, are thee other ways to specify a specific vs version? Even if this is done (very uncommon if ever) it still leaves the code system version unspecified so if a code system is updated then can the expansion used in the required binding change? How does maturity level effect this? IE": if the resource/element is normative - can the expansion change?