System theory

I have attempted to call attention to what is perhaps the weakest link in system theory, namely, the process of making measurements which yield the numbers that serve as the inputs to the mathematical theory. I have called attention to Dirac\´s notation because quantum mechanics, in which this notation was first used, is very much concerned with the measurement process and the notions of linear operators which are used therein have a very close tie to measurement problems in larger systems. Secondly, I have suggested that we need more invention and critical innovation in developing a notation well suite(d for the representation and study of systems. Here, vector-space concepts and matrix notation may be used to good advantage, and signal-flow graphs provide a new kind of algebraic notation that is well matched to the visual sense and deserves continued study. Finally, the links between the theory and the natural universe may be strengthened by extending the rich stockpile of abstract concepts downward to acquire ever fuller itnterpretations and insights into physical phenomena. Let us not forget Poincare\´s answer to the question, "Who has taught us the true analogies, the profound analogies which the eyes do not see, but which reason can divine? It is the mathematical mind, which scorns content and clings to pure form."