Achievable behavior by composition

A fundamental question in systems and control theory concerns the characterization of the set of achievable closed-loop systems for a given plant system and a controller system to be designed. This problem, for example, shows up in assessing the 'limits of performance' of a controlled system. Similar problems have been studied by researchers in automata theory and discrete event systems replacing the notion of closed-loop system by the composition of a given system and its controller. In this paper this problem is addressed in a general behavioral context. Necessary and often sufficient conditions for a behavior to be achievable are given, and for any achievable behavior a canonical controller is defined. These results generalize previously obtained results obtained for finite-dimensional linear systems. Next these general results are applied to classes of automata and hybrid systems.