An Interface cannot have StateMachines, except a protocol StateMachine.
A state machine defines the behavior of an instantiated classifier; therefore it cannot define an interface.
Since an interface specifies conformity characteristics, it does not own detailed behavior specifications. Instead, interfaces may own a protocol state machine that specifies event sequences and pre/post conditions for the operations described by the interface.
- Move the state machine to an instantiable Classifier.
- Modify the state machine to define it as a protocol state machine.