Comment:

The meaning or intended use of this element is not clear. For example : "no match in the mappings: What is a match in a mapping? Note - the terminology bindings info on the concept map page http://hl7.org/fhir/2018Jan/conceptmap.html#def has a text definition of 'defines what action to take if there is no match in the group' - should this be 'map' for one of the source codes in the group? Assume group.target.equivalence code of unmatched covers the case where a source code/code system cannot be mapped to a concept in the target code system - is the unmapped element meant to provide a map when there isn't really a map from the source code to a code in the target code system system or is it unmapped guidance or something else? The text is very sparse and it is difficult to understand - especially with the wording 'no match in the mappings'

Summary:

ConceptMap.group.unmapped : What to do when there is no match in the mappings in the group.