Repeating: the MSM/Statechart overlap in features and interface is quite unique to Boost.
They definitely overlap in features and also in intent, but my understanding is that the interfaces are vastly different, and that's an important distinguishing feature. Am I missing something?
No you aren't. At first look, they seem similar, but as soon as you concretely start writing a state machine with both libraries, like Juraj could tell you (he did it), you'll start seeing that the differences are there. Of course, both use states, events and transitions but that's about all. MSM bases itself on the transition table, while with Statechart, the user writes his decisions in the react function. Composites are full state machines with MSM, a simple state with Statechart. MSM uses more metaprogramming, Statechart follows a solution with multiple translation units. Etc. etc. The point is, the interfaces differ, the normal usage even more and the "correct" way to use each (in the authors' eyes) much more as both follow a completely different philosophy, as many heated discussions showed. Christophe