We agree with the submitter that this needs to be clarified and described in the specification - likely in the discussion of [binding strength] ( http://hl7.org/fhir/terminologies.html#strength ). Also need to explicitly reference the [maxValueSet] ( http://hl7.org/fhir/extension-elementdefinition-maxvalueset.html ) extension. The maturity of maxValueSet is currently 1, so it is not clear how that can be included as part of the normative specification (probably needs a separate tracker). Will add a new subsection under  4.1.4 Controlling the use of Coded Values ( http://hl7.org/fhir/terminologies.html#binding)  to describe the use of this extension.  Will also move Binding Strength under 4.1.4 as a subsection, and it should appear before the max binding subsection.