Change performer to: performer 0..* role 0..1 CodeableConcept (steal vocabulary from Procedure) actor 1..1 Reference(Practitioner|RelatedPerson|Patient|Device|Organization) onBehalfOf 0..1 Organization Add note to work groups that they may replace with performer 0..* Reference(...) or performer 0..1 Reference(...) if that's more appropriate. (E.g. AllergyIntolerance) Will also note that the more complex structure should be used if there's a need to associate Practitioner with Organization in the context of a specific event Add invariant prohibiting onBehalfOf if actor is Patient or Device