http://hl7.org/fhir/StructureDefinition/workflow-followOnOf|5.2.0

Points to a preceding event within a workflow that was a prerequisite for or provides other justification for the current action.

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