Figure 2

Method of counting transitions. If we count all active state to active state transitions between variable pairs as shown in (a), there will be 5 transitions from variable A to B. This method assumes that every phase in which a variable is active is independent of its previous phase(s). If we assume that variables are activated in blocks, i.e. first activated at a particular time and then self-sustained for a duration, then it becomes reasonable to count transition frequencies as shown in (b). In (b), transitions always result in a variable’s first activation. We count two A to B transitions and one B to A transition.