Well it is OK to stack state machines as long as state transitions are not enqueued regardless which state machine is "active". In case of the event structure inside the "sub-system": Gerd already mentioned that the event structure is already armed even if the "sub-system" is not "active". Once you enter the state in the top-level state machine which contains the "sub-system", the event queue will be worked on.
Therefore, it is easier for you as developer to design a flat structure of "events" which means that you should try to "unfold" your inner state machine by adding the cases in a common sense in the top-level state machine.
Norbert
Norbert
----------------------------------------------------------------------------------------------------
CEO: What exactly is stopping us from doing this?
Expert: Geometry
Marketing Manager: Just ignore it.
