[wvanbergen]

My post isn't meant as a description about state machines; I point to wikipedia for that. The Ruby gem also gives a very nice introduction indeed.

However, the point I try to make is very much about state machines, because modelling state using a state machine, forces you to think about all possible state transitions. This will make it less likely that you application will get into an unexpected state. Also, keeping an audit trail is very much about state transitions, because the transitions describe the behavior of the system, not the state itself.