In striving to provide the simplest possible definition of a process, while providing as much functionality as possible, the impact of various trade-offs must be evaluated carefully.
This paper has identified a number of the more important aspects of functionality and has discussed the issues and trade-offs involved, particularly in terms of the simplest mechanisms that can be used to provide the needed functionality.
By providing the necessary functionality from the start, it is possible to avoid the problems associated with piecemeal evolution. In this regard, it is instructive to compare the complex definition of a process offered by UNIX System V to the simple, but incomplete, definition offered by early versions of UNIX.
