40 MODULARITY $3.I "module"will denote the basic unit of decomposition of our systems,whatever it actually is.If you are familiar with non-object-oriented methods you will probably think of the subroutines present in most programming and design languages,or perhaps of packages as present in Ada and (under a different name)in Modula.The discussion will lead in a later chapter to the O-O form of module-the class-which supersedes these ideas.If you have encountered classes and O-O techniques before,you should still read this chapter to understand the requirements that classes address,a prerequisite if you want to use them well. 3.1 FIVE CRITERIA A design method worthy of being called "modular"should satisfy five fundamental requirements,explored in the next few sections: ·Decomposability. ·Composability. ·Understandability. ·Continuity. ·Protection. Modular decomposability A software construction method satisfies Modular Decomposability if it helps in the task of decomposing a software problem into a small number of less complex subproblems,connected by a simple structure,and independent enough to allow further work to proceed separately on each of them The process will often be self-repeating since each subproblem may still be complex enough to require further decomposition. Decomposabil- y40 MODULARITY §3.1 “module” will denote the basic unit of decomposition of our systems, whatever it actually is. If you are familiar with non-object-oriented methods you will probably think of the subroutines present in most programming and design languages, or perhaps of packages as present in Ada and (under a different name) in Modula. The discussion will lead in a later chapter to the O-O form of module — the class — which supersedes these ideas. If you have encountered classes and O-O techniques before, you should still read this chapter to understand the requirements that classes address, a prerequisite if you want to use them well. 3.1 FIVE CRITERIA A design method worthy of being called “modular” should satisfy five fundamental requirements, explored in the next few sections: • Decomposability. • Composability. • Understandability. • Continuity. • Protection. Modular decomposability The process will often be self-repeating since each subproblem may still be complex enough to require further decomposition. A software construction method satisfies Modular Decomposability if it helps in the task of decomposing a software problem into a small number of less complex subproblems, connected by a simple structure, and independent enough to allow further work to proceed separately on each of them Decomposabil￾ity