This is the ValueSet that contains all the codes in MessageDefinitionIdentifierSystemValueset (http://medcomfhir.dk/ig/terminology/ValueSet/medcom-messagedefinition-identifer-system-valueset) and MessageDefinitionIdentifierSystemValueset (http://medcomfhir.dk/ig/terminology/ValueSet/medcom-messagedefinition-identifer-system-valueset). E.g. what you have to deal with if you get resources containing codes in either of them