The following example illustrates an inpatient encounter reference.

define "Inpatient Encounter":
  [Encounter: "Encounter Inpatient"] EncounterInpatient
    where EncounterInpatient.status = 'finished'
      and "LengthInDays"(EncounterInpatient.period) <= 120
      and EncounterInpatient.period ends during "Measurement Period"