Each Use Case has zero to many exception courses. The exception course is a sequence of steps that the Role or Actor takes when the task is interrupted or a single postcondition that validates the exception course was taken. The exception course indicates the cause of the interruption, then indicates how the Role or Actor recovers. Exception courses must provide at least a postcondition for the step that validates the exception course that was taken. The postcondition that validates the goal of the Use Case is not necessarily true after the exception course has been taken. The title of each exception course should appear exactly as it is in cross-referencing Basic Course step.