Source:http://linkedlifedata.com/resource/umls/id/C1550456
HL7V3.0: <p><b>Definition:</b> One of a set of acts that specify an option for the property values that the parent act may have. Typically used in definitions or orders to describe alternatives. An option can only be used as a group, that is, all assigned values must be used together. The actual mood of the act is the same as the parent act, and they must be linked by an actrelationship with type = OPTN.</p>