This chapter has presented some of the general background and motivation of SETL, and suggested why it remains a language worthy of further study and development.
Since data processing is largely concerned with the interaction of programs with their environments, the next chapter examines the rich repertoire of input/output and related facilities that have been added to SETL. Subsequent chapters deal with the more network-specific provisions, and illustrate the design patterns I have found most effective in the use of these new tools.