“…Thus, it may happen that on the one hand, we have an indeterministic execution of an action, e.g. w 1 , w 2 , e ∈ Step and w 1 , w 3 , e ∈ Step (w 2 = w 3 ), and, on the other hand, that the same transition is a result of the execution of two different 3 Indeed, an action frame can be seen as a labelled transition system as described in [14]. In the action model we do not really take advantage of the information about the final state of the transitions.…”