My (admittedly limited) experience had some high-cohesion models and it worked ok, with the caveat that they often didn't change independently. It was basically

My (admittedly limited) experience had some high-cohesion models and it worked ok, with the caveat that they often didn't change independently. It was basically one FSM for a cluster of high-cohesion objects, and the events would mutate some subset. I agree with your colleague somewhat. If you have a system where every domain object is inextricably linked to every other domain object, then you're going to have a state explosion trying to capture the states and transitions. My gut reaction looking at a system like that is to start decomposing it, looking for accidental coupling that doesn't need to be there.