> All I could think of was the rigid hierarchy problem found in OOP- what if your transitions don’t neatly fit in hierarchies Yes, HSMs are very rigid. It's on

> All I could think of was the rigid hierarchy problem found in OOP- what if your transitions don’t neatly fit in hierarchies Yes, HSMs are very rigid. It's one of the few downsides (which I admit as a Harel state chart fanboy)[0]. However, the particular problem you address can be handled by cross-hierarchy events, i.e. one state emits an event, and some other state elsewhere handles it. Plus, of course, not everything is nested; you have orthogonal regions, too. [0] One interpretation of this rigidity is that it represents the requirements faithfully and compact (YAGNI), so you don't have a level of abstraction that could be used to soften the blows of further requirement changes.