Re: [Boost-users] [statechart ] UML2.0 local transitions and history

From: Tim Milward (tim.milward_at_[hidden])
Date: 2006-05-08 17:40:00

> Ok, I misunderstood how local transitions work. An innermost state where 
> any of its direct *or* *indirect* outer states define local transitions 
> behaves as if all those local transitions originated at the state 
> itself. I guess we'll have to go the sc::local_transition / 
> sc::simple_state::transit_locally route then...

It seems I'm the one who misunderstood. I've dug a little deeper and 
your are right that the difference between local and external is just 
one level of entry/exit actions. So your approach of adding an 
intermediate state does work.

 From the UML specs it's hard to extract the exact definition of a local 
transition. 
http://www.johndeacon.net/UML/UML_Appendix/Generated/UML_Appendix_behavioral.asp 
discusses this subject and warns about the pitfalls of using composite 
states to de-clutter a state machine.

[I think there is a more general concept here, the same as having an nth 
level history, a transition could have a level specification, n=0 is 
external, n=1 is local, and n=infinity is the way I misinterpreted local 
transitions. I need some real practical examples ...]