So, more often than not, you'll catch your state machines attaching behavior directly to your objects. Which sometimes bugs you, because you want your states to

So, more often than not, you'll catch your state machines attaching behavior directly to your objects. Which sometimes bugs you, because you want your states to be less about "nouns" and more about "verbs". And eventually you notice that, in most cases, you crave coordination across those "nouns" (e.g.: "a transition in model A provokes a transition in model B"). The real workflow now lies "at the intersection of two models". You start to wish for the equivalent of "process management" in addition to state management. So this, coupled with general unhappiness for the sort of anti-modular/anti-abstraction problem you see in state machines, might incite you to look at "workflow engines" like Ruote. http://ruote.rubyforge.org/ http://ruote.rubyforge.org/ TL;DR I am drinking the 'ruote' kool-aid right now. Augment your state machines with a great coordinator in the sky, a few levels higher in the architecture stack. (BTW: I'm paraphrasing this argument from John Mettraux's "state machine != workflow engine" post, and Kenneth Kalmer's Ruote presentation from this year. Really changed my thoughts on the matter recently.)