ABSTRACT
A fundamental problem in science and engineering is to predict the effect a particular action will have on a physical system. This problem can be posed more precisely as follows. What will be the response, y(t), for all times t in the interval t0 ≤ t < tf , of a specified system to an arbitrary input u(t) over the same time interval (t0 ≤ t < tf )? Because the question involves the future behavior of the system, its answer requires some sort of model of the system.
