Acknowledgments

The authors would like to acknowledge and thank John Altinbay, Jim Heumann, and Dan Rawsthorne for their careful and insightful reviews of this second edition. We'd also to thank the many others who contributed to this work, including Al Davis, Ed Yourdon, Grady Booch, Philippe Kruchten, Leslee Probasco, Ian Spence, Jean Bell, Walker Royce, Joe Marasco, Elemer Magaziner, and the following reviewers of the first edition: Ag Marsonia, Frank Armour, Dr. Ralph R. Young, Professor David Rine, and Dan Rawsthorne.

We admit that without their insightful comments, we could not have written a worthy work. In addition, we'd like to thank Kim Arney Mulcahy and the editors and support staff at Addison-Wesley, who tuned our work in process and helped it become a tangible product, like the "rock" described in the Foreword. Lastly, we must again thank our loving families for supporting all the " heads-down weekends" necessary to complete this second edition.

Preface to the First Edition

By Dean Leffingwell, 1999

Context

The knowledge delivered in this book represents the cumulative experience of a number of individuals who have spent their careers defining, developing, and delivering world-class software systems. This book is not an academic treatment of requirements management. During the 1980s, Don Widrig and I were executives in a small company producing software solutions for customers. When we developed many of the requirements management practices described in this book, our perspective was of those accountable for both the outcomes of the software systems we developed and the results that had to be delivered to shareholders. As the performance of the delivered software was critical to the success of the business venture itself, we tended to discourage petty biases, personal preferences, and experimentation with unproven techniques.

Over the past decade , the techniques have evolved and have been enhanced by new experiences, extended with the help of additional expertise, in different companies and in different circumstances. But all of the techniques presented are "real-world" proven and have withstood the test of time. Perhaps even more important, they have withstood the technological change that has occurred in the industry during this period. Indeed, most of the principles in this book are independent of changing trends in software technology. We can therefore at least hope that the knowledge expressed herein can deliver some lasting value.

Requirements Lessons from Building Software for Others

At first, I just hated computers. ("What? I stayed here all night and I have to submit this batch job again because I left out a 'space'? Are you crazy? Let me in that room. . . .") My first "real computer" was a minicomputer, which, although incredibly limited in performance by today's standards, was unique in that I could touch it, program it, and make it do what I wanted. It was mine .

My early research applied the computer to analyze physiological signals from the human body, primarily EKGs, and the dedicated computer was a wonderful tool for this job. Out of this experience, I began to apply my programming skills and experience with real-time software systems to the needs of the industry.

Eventually, I incorporated RELA, Inc., and began a long, and perhaps unusually difficult, career as CEO of a contract software development business. My coauthor, Don Widrig, joined me at RELA in the early years as Vice President of Research and Development. He had the primary accountability for the success of the many systems that we developed.

Over the years, the company grew rapidly . Today, the company employs many hundreds of people and has diversified beyond providing just software to providing complete medical devices and systems that encompass software, as well as mechanical, electronic, optical, and fluidics-handling subsystems. However, at the heart of each and every machine, including the latest DNA fingerprinting in-vitro diagnostic clinical laboratory, lies one or more computers, reliably and routinely delivering their steady heartbeats through the rhythm of a real-time multitasking system.

Initially, we would program anything for anybody, from antenna-positioning software to such games as laser tag, automated guided vehicles for amusement parks, educational products, welding robots, and automated machine controls. We even developed a large distributed computer system that automatically detected and counted the presence of commercials on television. (Our motto then was "We make computers to watch commercials so you don't have to!") Perhaps the only thing the software we developed had in common was that we developed it for others ”we were not domain experts in the field, and we couldn't cover our own paychecks if we had to. We were completely dependent on the customer's satisfaction as the final determination of outcome . In many ways, such an environment was very conducive to effective requirements management. Here's why:

We knew little about the domain, so we were dependent on customers for the requirements. There was little temptation to make them up; we had to ask, and we had to learn how to ask the right questions the right way, at the right time.
Our customers often knew little about computers, so they were dependent on us to translate their needs and wishes into technical requirements.
The fact that money changed hands created a rigorous interface between the developer and the customer.
Quality was easy to measure: We either got paid or we didn't.

Big Question 1: "Exactly what is this software supposed to do?"

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It was in this environment that we discovered the first of two fundamental questions that face software developers on each and every project. This question dominated our behavior for many years and remains today as perhaps the toughest question to answer in any software project. And the Big Question is:

So, exactly what is this software supposed to do?

The principles and techniques presented in Team Skill 1, Analyzing the Problem; Team Skill 2, Understanding User and Stakeholder Needs; and Team Skill 3, Defining the System, were developed over more than a decade as a means to discover the answer to this question. Each of these techniques has proved its worth and has demonstrated its effectiveness in many real-world projects. It was also during this period that I first became aware of the work of Donald Gause and Jerry Weinberg, especially their book Exploring Requirements: Quality Before Design (1989). Because their book heavily influenced our work, we have borrowed a few key concepts from it for this book, both because the concepts work and because we thought it only fair that you share the Gause and Weinberg experience.

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Leffingwell D., Widrig D.

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