Title Just Enough Structured Analysis (Yourdon).pdf ✅

www.yourdon.com ©2006 Ed Yourdon - rev. 051406 Chances are that you groaned when you first picked up this book, seeing how heavy and thick it was. The prospect of reading such a long, technical book is enough to make anyone gloomy; fortunately, just as long journeys take place one day at a time, and ultimately one step at a time, so long books get read one chapter at a time, and ultimately one sentence at a time. 1.1 Why is systems analysis interesting? Long books are often dull; fortunately, the subject matter of this book — systems analysis — is interesting. In fact, systems analysis is more interesting than anything I know, with the possible exception of sex and some rare vintages of Australian wine. Without a doubt, it is more interesting than computer programming (not that programming is dull) because it involves studying the interactions of people, and disparate groups of people, and computers and organizations. As Tom DeMarco said in his delightful book, Structured Analysis and Systems Specification (DeMarco, 1978), [systems] analysis is frustrating, full of complex interpersonal relationships, indefinite, and difficult. In a word, it is fascinating. Once you’re hooked, the old easy pleasures of system building are never again enough to satisfy you. This may come as a surprise to you if you have any experience writing computer programs. [1] Programming is enormous fun, and it’s enormously satisfying to see a program execute successfully, especially after spending several hours debugging it. It’s hard to imagine that things could be even more rewarding and exciting when you begin to move away from the computer and the writing of computer programs to study the overall system in which the programs play a part. But by the end of this book, I hope to have convinced you that the real challenge, and the real joy, of working with computer systems is that of carrying out systems analysis. No matter what profession you decide to pursue, it will be important for you to understand what systems analysis is all about. If you work in the computer industry as something other than an electrical engineer or hardware designer, there is a good chance that your career will progress from programmer to systems designer to systems analyst before you finally move on to the ranks of management. [2] In this chapter, you will learn: 1. Why systems analysis is interesting; 2. Why systems analysis is more difficult than programming; and 3. Why it is important to be familiar with systems analysis. 2
www.yourdon.com ©2006 Ed Yourdon - rev. 051406 1.2 Whom this book is intended for This book is intended for two audiences: first, the person who is new to the field of systems analysis, and, second, the experienced systems analyst who needs to acquaint himself with systems modeling tools and techniques that have evolved over the past decade. Many readers will be university computer science students who have completed earlier courses on computer programming; some may be students in a business training program. However, the book should be equally readable by people who have finished their university training and who are now working in industry. Many people in the computer industry spend their first several years working as a computer programmer, and then suddenly find themselves promoted to a position of systems analyst, without ever being told what systems analysis is all about or what a systems analyst does. If you are in such a position, this book is for you. You should also find the book useful if you began working as a systems analyst in the 1970s or 1980s and never had an opportunity to learn about classical analysis methods such as structured analysis, or the newer methods such as object-oriented analysis. More and more often today, people outside the computer profession are finding it necessary to become familiar with the field of systems analysis. If you are a business person or a manager, there is a good chance that you will be involved in a systems analysis activity. You will have systems analysts working for you, spending their time trying to understand what kind of automated system you want them to build. Similarly, if you are an administrator, a clerk, a scientist, a politician, an engineer, or an accountant — or virtually any other professional in today’s society — there is a good chance that you will spend a significant amount of time during your career interacting with systems analysts who will be designing and specifying sophisticated computer systems for you. The more you know about what these people do, and what they expect of you, the better off you will be. Even if you have no expectation of working in a white collar job — that is, even if you expect to be an artist, a writer, a musician, or an athlete — you should know what systems analysis is all about. Citizens in every walk of life are affected by computer systems of all sorts. Even if you never intend to build a computer system or have one built for you, it is inevitable that you will be using computer systems for your banking, for your education, for your interactions with the IRS and Social Security, and for virtually every aspect of your interactions with modern society. As John Gall says in Systemantics (Gall, 1977), No one, these days, can avoid contact with systems. Systems are everywhere: big systems, little systems, systems mechanical and electronic, and those special systems that consist of organized associations of people. In self- defense, we must learn to live with systems, to control them lest they control us. As Humpty Dumpty said to Alice (though in another context): “The question is: which is to be master — that’s all.” To emphasize this point even more, keep in mind that the computer industry represented approximately 8% of the United States GNP in 1985; by 1990, it was expected to represent as much as 15% of the GNP. [3] Almost every product built today by American business has one or more computers embedded within it, and almost every service provided to the marketplace by American business is based on or controlled by a computer system. 3