Some Applications

Abstract

In this chapter we shall illustrate some of the applications of the abstract principles we stated in the previous chapter to specific concrete problems. Our aim is to show the usefulness of the abstract language in formulating and answering specific questions, identifying their specific characteristics and recognizing common features of problems that a priori are very different. Of course, the abstract approach mostly follows and is motivated by concrete questions, but later we see the approach as the most direct way to understand many questions, and even the most natural.