The model deals with a set of two types of aging or non-aging elements such that the nature of the new element depends on the nature of the element to be renewed and on that of its neighbours. A Monte Carlo simulation of the time-evolution of the set shows that a patchwise topography can or cannot appear according to the space-interactions between neighbours, which can be stable or not according to the time-interactions between the generating element and the new element. In electrochemistry, the elements of the set are identified with adsorbed species, at an ideal interface, appearing, for instance, during two competitive reaction paths. Relations are established between the local reaction rates and the probabilities that a path is followed, and its duration. Mechanistic implications (catalysis, activation by feedback) as well as some examples of such a patchwise topography are discussed.