An encounter activity (templateId 2.16.840.1.113883.10.20.1.21) SHALL be represented with Encounter. The value for "Encounter / classCode" in an encounter activity SHALL be “ENC” 2.16.840.1.113883.5.6 ActClass STATIC. The value for "Encounter / moodCode" in an encounter activity SHALL be “EVN” 2.16.840.1.113883.5.1001 ActMood STATIC. An encounter activity SHALL contain at least one Encounter / id. An encounter activity MAY contain exactly one Encounter / effectiveTime, to indicate date, time, and/or duration of an encounter. An encounter activity MAY contain one or more Encounter / entryRelationship, whose value for “entryRelationship / typeCode” SHALL be “RSON” “Has reason” 2.16.840.1.113883.5.1002 ActRelationshipType STATIC, where the target of the relationship represents the indication for the activity. Encounter / performer MAY contain exactly one Encounter / performer / assignedEntity / code, to define the role of the practioner. An encounter activity SHOULD contain exactly one Encounter / code.