Creation Event

An Event that causes the creation of a new Instance of a Class is a creation event. This type of Event may only appear on Lifecycle State Models and is never polymorphic.

(See also figure at Deletion State description)

When a Creation Event occurs, it causes a new instance of its Class to be created in the designated Non Deletion State. Any parameter values delivered with that event are provided as input to the new Destination State’s Activity executing on the newly created instance.

A Creation Event is typically shown on a UML state machine diagram next to an arrow leading from the UML initial pseudo-state symbol toward an initial Non Deletion State.

Why must a Creation Event be monomorphic? Consider a bank account example. You might want to send a poolymorphic Close signal to an instance of Account without knowing or caring whether it is checking or savings, even though the resultant behavior might be handled in only one subclass. But you wouldn't ever try to create an instance of Account without knowing the subclass in advance. Otherwise you would create only a portion of the instance, which is not possible.