Chapter 1 : Software and software engineering

Chapter 1 : Software and software engineering

He had the classic look of a senior executive for a major software company—mid-40s, slightly graying at the temples, trim and athletic, with eyes that penetrated the listener as he spoke. But what he said shocked me. “Software is dead.” I blinked with surprise and then smiled. “You’re joking, right? The world is driven by software and your company has profited handsomely because of it. It isn’t dead! It’s alive and growing.” He shook his head emphatically. “No, it’s dead . . . at least as we once knew it.” I leaned forward. “Go on.” He spoke while tapping the table for emphasis. “The old-school view of software—you buy it, you own it, and it’s your job to manage it—that’s coming to an end. Today, with Web 2.0 and pervasive computing coming on strong, we’re going to be seeing a completely different generation of software. It’ll be delivered via the Internet and will look exactly like it’s residing on each user’s computing device . . . but it’ll reside on a far-away server.”

QUICK LOOK

What is it? 

Computer software is the product that software professionals build and then support over the long term. It encompasses programs that execute within a computer of any size and architecture, content that is presented as the computer programs execute, and descriptive information in both hard copy and virtual forms that encompass virtually any electronic media. Software engineering encompasses a process, a collection of methods (practice) and an array of tools that allow professionals to build highquality computer software. 

Who does it? 

Software engineers build and support software, and virtually everyone in the industrialized world uses it either directly or indirectly. Why is it important? Software is important because it affects nearly every aspect of our lives and has become pervasive in our commerce, our culture, and our everyday activities.Software engineering is important because it enables us to build complex systems in a timely manner and with high quality. 

What are the steps? 

You build computer software like you build any successful product, by applying an agile, adaptable process that leads to a high-quality result that meets the needs of the people who will use the product. You apply a software engineering approach. 

What is the work product? 

From the point of view of a software engineer, the work product is the set of programs, content (data), and other work products that are computer software. But from the user’s viewpoint, the work product is the resultant information that somehow makes the user’s world better. 

How do I ensure that I’ve done it right? 

Read the remainder of this book, select those ideas that are applicable to the software that you build, and apply them to your work.

I had to agree. “So, your life will be much simpler. You guys won’t have to worry about five different versions of the same App in use across tens of thousands of users.” He smiled. “Absolutely. Only the most current version residing on our servers. When we make a change or a correction, we supply updated functionality and content to every user. Everyone has it instantly!” I grimaced. “But if you make a mistake, everyone has that instantly as well.” He chuckled. “True, that’s why we’re redoubling our efforts to do even better software engineering. Problem is, we have to do it ‘fast’ because the market has accelerated in every application area.” I leaned back and put my hands behind my head. “You know what they say, . . . you can have it fast, you can have it right, or you can have it cheap. Pick two!” “I’ll take it fast and right,” he said as he began to get up. I stood as well. “Then you really do need software engineering.” “I know that,” he said as he began to move away. “The problem is, we’ve got to convince still another generation of techies that it’s true!”

Is software really dead? If it was, you wouldn’t be reading this book! Computer software continues to be the single most important technology on the world stage. And it’s also a prime example of the law of unintended consequences. Fifty years ago no one could have predicted that software would become an indispensable technology for business, science, and engineering; that software would enable the creation of new technologies (e.g., genetic engineering and nanotechnology), the extension of existing technologies (e.g., telecommunications), and the radical change in older technologies (e.g., the printing industry); that software would be the driving force behind the personal computer revolution; that shrink-wrapped software products would be purchased by consumers in neighborhood malls; that software would slowly evolve from a product to a service as “on-demand” software companies deliver just-in-time functionality via a Web browser; that a software company would become larger and more influential than almost all industrial-era companies; that a vast software-driven network called the Internet would evolve and change everything from library research to consumer shopping to political discourse to the dating habits of young (and not so young) adults. No one could foresee that software would become embedded in systems of all kinds: transportation, medical, telecommunications, military, industrial, entertainment, office machines, . . . the list is almost endless. And if you believe the law of unintended consequences, there are many effects that we cannot yet predict. No one could predict that millions of computer programs would have to be corrected, adapted, and enhanced as time passed. The burden of performing these “maintenance” activities would absorb more people and more resources than all work applied to the creation of new software. As software’s importance has grown, the software community has continually attempted to develop technologies that will make it easier, faster, and less expensive

PREFACE of SE [Software Engineering]

When computer software succeeds—when it meets the needs of the people who use it, when it performs flawlessly over a long period of time, when it is easy to modify and even easier to use—it can and does change things for the better. But when software fails—when its users are dissatisfied, when it is error prone, when it is difficult to change and even harder to use—bad things can and do happen. We all want to build software that makes things better, avoiding the bad things that lurk in the shadow of failed efforts. To succeed, we need discipline when software is designed and built. We need an engineering approach. It has been almost three decades since the first edition of this book was written. During that time, software engineering has evolved from an obscure idea practiced by a relatively small number of zealots to a legitimate engineering discipline. Today, it is recognized as a subject worthy of serious research, conscientious study, and tumultuous debate. Throughout the industry, software engineer has replaced programmer as the job title of preference. Software process models, software engineering methods, and software tools have been adopted successfully across a broad spectrum of industry segments. Although managers and practitioners alike recognize the need for a more disciplined approach to software, they continue to debate the manner in which discipline is to be applied. Many individuals and companies still develop software haphazardly, even as they build systems to service today’s most advanced technologies. Many professionals and students are unaware of modern methods. And as a result, the quality of the software that we produce suffers, and bad things happen. In addition, debate and controversy about the true nature of the software engineering approach continue. The status of software engineering is a study in contrasts. Attitudes have changed, progress has been made, but much remains to be done before the discipline reaches full maturity. The seventh edition of Software Engineering: A Practitioner’s Approach is intended to serve as a guide to a maturing engineering discipline. Like the six editions that preceded it, the seventh edition is intended for both students and practitioners, retaining its appeal as a guide to the industry professional and a comprehensive introduction to the student at the upper-level undergraduate or first-year graduate level. The seventh edition is considerably more than a simple update. The book has been revised and restructured to improve pedagogical flow and emphasize new and important software engineering processes and practices. In addition, a revised and updated “support system,” illustrated in the figure, provides a comprehensive set of student, instructor, and professional resources to complement the content of the book. These resources are presented as part of a website (http://software-engineer-technical.blogspot.com/) specifically designed for Software Engineering: A Practitioner’s Approach. The Seventh Edition. The 32 chapters of the seventh edition have been reorganized into five parts. This organization, which differs considerably from the sixth edition, has been done to better compartmentalize topics and assist instructors who may not have the time to complete the entire book in one term.

Part 1, The Process, presents a variety of different views of software process, considering all important process models and addressing the debate between prescriptive and agile process philosophies. Part 2, Modeling, presents analysis and design methods with an emphasis on object-oriented techniques and UML modeling. Pattern-based design and design for Web applications are also considered. Part 3, Quality Management, presents the concepts, procedures, techniques, and methods that enable a software team to assess software quality, review software engineering work products, conduct SQA procedures, and apply an effective testing strategy and tactics. In addition, formal modeling and verification methods are also considered. Part 4, Managing Software Projects, presents topics that are relevant to those who plan, manage, and control a software development project. Part 5, Advanced Topics, considers software process improvement and software engineering trends. Continuing in the tradition of past editions, a series of sidebars is used throughout the book to present the trials and tribulations of a (fictional) software team and to provide supplementary materials about methods and tools that are relevant to chapter topics. Two new appendices provide brief tutorials on UML and object-oriented thinking for those who may be unfamiliar with these important topics.

xxvi PREFACE

Web resources (1,000+ links) Reference library (500+ links) Checklists Work product templates Tiny tools Adaptable process model Umbrella activities task set Comprehensive case study

Student resources

Instructor resources

Solved problems

Instructor manual

Test bank

Industry comment

Distance learning

Professional resources

Powerpoint slides

Practice quizzes

Other SE topics

SEPA 7/e

Chapter study guides

Support System for SEPA, 7/e

The five-part organization of the seventh edition enables an instructor to “cluster” topics based on available time and student need. An entire one-term course can be built around one or more of the five parts. A software engineering survey course would select chapters from all five parts. A software engineering course that emphasizes analysis and design would select topics from Parts 1 and 2. A testing-oriented software engineering course would select topics from Parts 1 and 3, with a brief foray into Part 2. A “management course” would stress Parts 1 and 4. By organizing the seventh edition in this way, Ihave attempted to provide an instructor with a number of teaching options. In every case, the content of the seventh edition is complemented by the following elements of the SEPA, 7/e Support System. Student Resources. A wide variety of student resources includes an extensive online learning center encompassing chapter-by-chapter study guides, practice quizzes, problem solutions, and a variety of Web-based resources including software engineering checklists, an evolving collection of “tiny tools,” a comprehensive case study, work product templates, and many other resources. In addition, over 1000 categorized Web References allow a student to explore software engineering in greater detail and a Reference Library with links to over 500 downloadable papers provides an in-depth source of advanced software engineering information. Instructor Resources. A broad array of instructor resources has been developed to supplement the seventh edition. These include a complete online Instructor’s Guide (also downloadable) and supplementary teaching materials including a complete set of over 700 PowerPoint Slides that may be used for lectures, and a test bank. Of course, all resources available for students (e.g., tiny tools, the Web References, the downloadable Reference Library) and professionals are also available. The Instructor’s Guide for Software Engineering: A Practitioner’s Approach presents suggestions for conducting various types of software engineering courses, recommendations for a variety of software projects to be conducted in conjunction with a course, solutions to selected problems, and a number of useful teaching aids. Professional Resources. A collection of resources available to industry practitioners (as well as students and faculty) includes outlines and samples of software engineering documents and other work products, a useful set of software engineering checklists, a catalog of software engineering (CASE) tools, a comprehensive collection of Web-based resources, and an “adaptable process model” that provides a detailed task breakdown of the software engineering process. When coupled with its online support system, the seventh edition of Software Engineering: A Practitioner’s Approach, provides flexibility and depth of content that cannot be achieved by a textbook alone. Acknowledgments. My work on the seven editions of Software Engineering: A Practitioner’s Approach has been the longest continuing technical project of my life. Even when the writing stops, information extracted from the technical literature continues to be assimilated and organized, and criticism and suggestions from readers worldwide is evaluated and cataloged. For this reason, my thanks to the many authors of books, papers, and articles (in both hardcopy and electronic media) who have provided me with additional insight, ideas, and commentary over nearly 30 years. Special thanks go to Tim Lethbridge of the University of Ottawa, who assisted me in the development of UML and OCL examples and developed the case study that accompanies this book, and Dale Skrien of Colby College, who developed the UML tutorial in Appendix 1. Their assistance and comments were invaluable. Special thanks also go to Bruce Maxim of the University of Michigan–Dearborn, who assisted me in developing much of the pedagogical website content that accompanies this book. Finally, I wish to thank the reviewers of the seventh edition: Their in-depth comments and thoughtful criticism have been invaluable.

 Osman Balci,
      Virginia Tech University Max Fomitchev,
      Penn State University Jerry (Zeyu) Gao,
      San Jose State University Guillermo Garcia,
      Universidad Alfonso X Madrid Pablo Gervas,
      Universidad Complutense de Madrid

SK Jain,
      National Institute of Technology Hamirpur Saeed Monemi,
      Cal Poly Pomona Ahmed Salem,
      California State University Vasudeva Varma,
      IIIT Hyderabad

The content of the seventh edition of Software Engineering: A Practitioner’s Approach has been shaped by industry professionals, university professors, and students who have used earlier editions of the book and have taken the time to communicate their suggestions, criticisms, and ideas. My thanks to each of you. In addition, my personal thanks go to our many industry clients worldwide, who certainly have taught me as much or more than I could ever teach them. As the editions of this book have evolved, my sons, Mathew and Michael, have grown from boys to men. Their maturity, character, and success in the real world have been an inspiration to me. Nothing has filled me with more pride. And finally, to Barbara, my love and thanks for tolerating the many, many hours in the office and encouraging still another edition of “the book.”