1 IntroductionrnA discrete dynamical system can be expressed as xn+1 = f(xn), n = 0, 1, 2,... where X is a metric space and f: X → X is a continuous map. The study of it tells us how the points in the base space X moved. Nevertheless, this is not enough for the researches of biological species, demography, numerical simulation and attractors (see [1], [2]). It is necessary to know how the subsets of X moved. In this direction, we consider the set-valued discrete system associated to f, An+1 = f(An), n = 0, 1, 2,... where f is the natural extension of f to K(X) (the class of all compact subsets of X).