A kinetic scheme is a network (a directed graph) of distinct states (although repetition of states may occur and this depends on the system), where each pair of states i and j are associated with directional rates, A i j (and A j i ). It is described with a master equation : a first-order differential equation for the probability P → → of a system to occupy each one its states at time t (element i represents state i). Written in a matrix form, this states: d P → → d t = A P → → , where A is the matrix of connections (rates) A i j .