http://hl7.org/fhir/StructureDefinition/event-basedOn|5.2.0

A plan, proposal or order that is fulfilled in whole or in part by this event.

element_id	types
Extension
Extension.extension
Extension.url
Extension.value[x]	Reference
Extension
Extension.id	http://hl7.org/fhirpath/System.String
Extension.extension	Extension
Extension.url	http://hl7.org/fhirpath/System.String
Extension.value[x]	Reference