A Role that can be played by either a Person or an Organization. The term "party" comes from the legal notion of persons or organizations being parties to a contract or parties to a transaction. The "party data model" (also called the "party pattern") is a common construct in database design, which allows one to reference persons or organizations the same way. The FHIM generally does not use this pattern, preferring to reference Roles which might be played by persons, animals, organizations, or inanimate objects. However, FHIR does use this pattern, by allowing references to a choice of different kinds FHIR Resources. Therefore, we have included this concept in order to facilitate alignment with FHIR. Note that this class contains two properties: a 0-1 association to Person (who may be a Patient, in which case, navigate to Patient via Person.asPatient), and a 0-1 association to Organization. These should be treated as an exclusive OR. Either the asPerson association OR the asOrganization association must be populated, but never both.