Over the past decade a new approach has been introduced to the theory of systems representations. Introduced by Jan C. Willems, it is called the "behavioural" approach. One of its main features is that it is well suited for modelling interconnections of systems. In this book, the author develops representation theory from a behavioural point of view and focuses on various types of ("generalized state space") first-order representations that commonly arise in the process of modelling. It covers minimality, derives transformation groups and offers realization methods that lead directly to minimal realizations. The book further presents generalized notions of controllability indices and observability indices and gives methods to calculate these indices. The book includes a procedure to derive a standard state space description from a general first-order representation. It fortifies the reader's understanding with basic examples from electrical networks and mechanics. Mathematicians and control engineers doing research on systems that are linear, time-invariant, deterministic, and finite dimensional should find this book a firm basis for understanding both the theory and applications of this behavioural approach.

This book is about the theory of system representations. The systems that are considered are linear, time-invariant, deterministic and finite dimensional. The observation that some representations are more suitable for handling a particular problem than others motivates the study of rep resentations. In modeling a system, a representation often arises naturally from certain laws that underlie the system. In its most general form the representation then consists of dynamical equations for the system compo nents and of constraint equations reflecting the connection between these components. Depending on the particular problem that is to be inves tigated, it will sometimes be useful to rewrite the equations, that is, to transform the representation. For this reason it is of special importance to derive transformations that enable one to switch from one representation to another. A new approach of the past decade has been the so-called "behavioral ap proach" introduced by Willems. One of the main features of the behavioral approach is that it is well suited for modeling the interconnection of sys tems. It is for this reason that the behavioral approach is a natural choice in the context of modeling. In this book we adopt the behavioral approach: we define a system as a "behavior," that is, a set of trajectories whose math ematical representation by means of differential or difference equations is nonunique. An aspect of this approach that is important in the context of representation theory is the fact that a natural type of equivalence arises."