Software Engineering by Roger Presmen

1. Software Engineering A P R A C T I T I O N E R S A P P R O A C H

2. McGraw-Hill Series in Computer Science Senior Consulting Editor C. L. Liu, National Tsing Hua University Consulting Editor Allen B. Tucker, Bowdoin College Fundamentals of Computing and Programming Computer Organization and Architecture Systems and Languages Theoretical Foundations Software Engineering and Databases Articial Intelligence Networks, Parallel and Distributed Computing Graphics and Visualization The MIT Electrical and Computer Science Series Software Engineering and Databases Atzeni, Ceri, Paraborschi, and Torlone, Database Systems, 1/e Mitchell, Machine Learning, 1/e Musa, Iannino, and Okumoto, Software Reliability, 1/e Pressman, Software Engineering: A Beginners Guide, 1/e Pressman, Software Engineering: A Practioners Guide, 5/e Ramakrishnan/Gehrke, Database Management Systems, 2/e Schach, Classical and Object- Oriented Software Engineering with UML and C++, 4/e Schach, Classical and Object- Oriented Software Engineering with UML and Java, 1/e

3. Software Engineering A P R A C T I T I O N E R S A P P R O A C H FIFTH EDITION Roger S. Pressman, Ph.D. Boston Burr Ridge, IL Dubuque, IA Madison, WI New York San Francisco St. Louis Bangkok Bogot Caracas Lisbon London Madrid Mexico City Milan New Delhi Seoul Singapore Sydney Taipei Toronto

4. SOFTWARE ENGINEERING Published by McGraw-Hill, an imprint of The McGraw-Hill Companies, Inc. 1221 Avenue of the Americas, New York, NY, 10020. Copyright/2001, 1997, 1992, 1987, 1982, by The McGraw-Hill Com- panies, Inc. All rights reserved. No part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written consent of The McGraw-Hill Companies, Inc., including, but not limited to, in any network or other electronic storage or transmission, or broadcast for distance learning. This book is printed on acid-free paper. 1 2 3 4 5 6 7 8 9 0 DOC/DOC 0 9 8 7 6 5 4 3 2 1 0 ISBN 0073655783 Publisher: Thomas Casson Executive editor: Betsy Jones Developmental editor: Emily Gray Marketing manager: John Wannemacher Project manager: Karen J. Nelson Production supervisor: Heather Burbridge Coordinator freelance design: Keith McPherson Supplement coordinator: Rose Range New media: Christopher Styles Cover design: Rhiannon Erwin Cover illustrator: Joseph Gilians Compositor: Carlisle Communications, Ltd. Typeface: 8.5/13.5 Leawood Printer: R. R. Donnelley & Sons Company Library of Congress Cataloging-in-Publication Data Pressman, Roger S. Software engineering: a practitioners approach / Roger S. Pressman.5th ed. p. cm. (McGraw-Hill series in computer science) Includes index. ISBN 0-07-365578-3 1. Software engineering. I. Title. II. Series. QA76.758.P75 2001 005.1dc21 00-036133 http://www.mhhe.com McGraw-Hill Higher Education A Division of The McGraw-Hill Companies

5. To my parents

6. vi Roger S. Pressman is an internationally recognized authority in software process improvement and software engineering technologies. For over three decades, he has worked as a software engineer, a manager, a professor, an author, and a consultant, focusing on software engineering issues. As an industry practitioner and manager, Dr. Pressman worked on the development of CAD/CAM systems for advanced engineering and manufacturing applications. He has also held positions with responsibility for scientic and systems programming. After receiving a Ph.D. in engineering from the University of Connecticut, Dr. Pressman moved to academia where he became Bullard Associate Professor of Computer Engineering at the University of Bridgeport and director of the university's Computer-Aided Design and Manufacturing Center. Dr. Pressman is currently president of R.S. Pressman & Associates, Inc., a consulting rm specializing in software engineering methods and training. He serves as principle consultant, helping companies establish effective software engineering practices. He also designed and developed the companys software engineering training and process improvement productsEssential Software Engineering, a complete video curriculum that is among the industry's most comprehensive treatments of the subject, and Process Advisor, a self- directed system for software engineering process improvement. Both products are used by hundreds of companies worldwide. Dr. Pressman has written many technical papers, is a regular contributor to industry periodicals, and is author of six books. In addition to Software Engineering: A Practitioner's Approach, he has written A Manager's Guide to Software Engineering (McGraw-Hill), an award-winning book that uses a unique Q&A format to present management guidelines for instituting and understanding software engineering technology; Making Software Engi- neering Happen (Prentice-Hall), the rst book to address the critical management problems associated with software process improvement; and Software Shock (Dorset House), a treat- ment that focuses on software and its impact on business and society. Dr. Pressman is on the Editorial Boards of IEEE Software and the Cutter IT Journal, and for many years, was editor of the Manager column in IEEE Software. Dr. Pressman is a well-known speaker, keynoting a number of major industry confer- ences. He has presented tutorials at the International Conference on Software Engineer- ing and at many other industry meetings. He is a member of the ACM, IEEE, and Tau Beta Pi, Phi Kappa Phi, Eta Kappa Nu, and Pi Tau Sigma. ABOUT THE AUTHOR

7. vii Preface xxv PART ONE The Product and the Process 1 CHAPTER 1 The Product 3 CHAPTER 2 The Process 19 PART TWO Managing Software Projects 53 CHAPTER 3 Project Management Concepts 55 CHAPTER 4 Software Process and Project Metrics 79 CHAPTER 5 Software Project Planning 113 CHAPTER 6 Risk Analysis and Management 145 CHAPTER 7 Project Scheduling and Tracking 165 CHAPTER 8 Software Quality Assurance 193 CHAPTER 9 Software Conguration Management 225 PART THREE Conventional Methods for Software Engineering 243 CHAPTER 10 System Engineering 245 CHAPTER 11 Analysis Concepts and Principles 271 CHAPTER 12 Analysis Modeling 299 CHAPTER 13 Design Concepts and Principles 335 CHAPTER 14 Architectural Design 365 CHAPTER 15 User Interface Design 401 CHAPTER 16 Component-Level Design 423 CHAPTER 17 Software Testing Techniques 437 CHAPTER 18 Software Testing Strategies 477 CHAPTER 19 Technical Metrics for Software 507 PART FOUR Object-Oriented Software Engineering 539 CHAPTER 20 Object-Oriented Concepts and Principles 541 CHAPTER 21 Object-Oriented Analysis 571 CHAPTER 22 Object-Oriented Design 603 CONTENTS AT A GLANCE

8. CONTENTS AT A GLANCEviii CHAPTER 23 Object-Oriented Testing 631 CHAPTER 24 Technical Metrics for Object-Oriented Systems 653 PART FIVE Advanced Topics in Software Engineering 671 CHAPTER 25 Formal Methods 673 CHAPTER 26 Cleanroom Software Engineering 699 CHAPTER 27 Component-Based Software Engineering 721 CHAPTER 28 Client/Server Software Engineering 747 CHAPTER 29 Web Engineering 769 CHAPTER 30 Reengineering 799 CHAPTER 31 Computer-Aided Software Engineering 825 CHAPTER 32 The Road Ahead 845

9. ix PART ONETHE PRODUCT AND THE PROCESS 1 CHAPTER 1 THE PRODUCT 3 1.1 The Evolving Role of Software 4 1.2 Software 6 1.2.1 Software Characteristics 6 1.2.2 Software Applications 9 1.3 Software: A Crisis on the Horizon? 11 1.4 Software Myths 12 1.5 Summary 15 REFERENCES 15 PROBLEMS AND POINTS TO PONDER 16 FURTHER READINGS AND INFORMATION SOURCES 17 CHAPTER 2 THE PROCESS 19 2.1 Software Engineering: A Layered Technology 20 2.1.1 Process, Methods, and Tools 20 2.1.2 A Generic View of Software Engineering 21 2.2 The Software Process 23 2.3 Software Process Models 26 2.4 The Linear Sequential Model 28 2.5 The Prototyping Model 30 2.6 The RAD Model 32 2.7 Evolutionary Software Process Models 34 2.7.1 The Incremental Model 35 2.7.2 The Spiral Model 36 2.7.3 The WINWIN Spiral Model 38 2.7.4 The Concurrent Development Model 40 2.8 Component-Based Development 42 2.9 The Formal Methods Model 43 2.10 Fourth Generation Techniques 44 2.11 Process Technology 46 2.12 Product and Process 46 2.13 Summary 47 REFERENCES 47 PROBLEMS AND POINTS TO PONDER 49 FURTHER READINGS AND INFORMATION SOURCES 50 TABLE OF CONTENTS

10. CONTENTSx PART TWOMANAGING SOFTWARE PROJECTS 53 CHAPTER 3 PROJECT MANAGEMENT CONCEPTS 55 3.1 The Management Spectrum 56 3.1.1 The People 56 3.1.2 The Product 57 3.1.2 The Process 57 3.1.3 The Project 57 3.2 People 58 3.2.1 The Players 58 3.2.2 Team Leaders 59 3.2.3 The Software Team 60 3.2.4 Coordination and Communication Issues 65 3.3 The Product 67 3.3.1 Software Scope 67 3.3.2 Problem Decomposition 67 3.4 The Process 68 3.4.1 Melding the Product and the Process 69 3.4.2 Process Decomposition 70 3.5 The Project 71 3.6 The W5HH Principle 73 3.7 Critical Practices 74 3.8 Summary 74 REFERENCES 75 PROBLEMS AND POINTS TO PONDER 76 FURTHER READINGS AND INFORMATION SOURCES 77 CHAPTER 4 SOFTWARE PROCESS AND PROJECT METRICS 79 4.1 Measures, Metrics, and Indicators 80 4.2 Metrics in the Process and Project Domains 81 4.2.1 Process Metrics and Software Process Improvement 82 4.2.2 Project Metrics 86 4.3 Software Measurement 87 4.3.1 Size-Oriented Metrics 88 4.3.2 Function-Oriented Metrics 89 4.3.3 Extended Function Point Metrics 91 4.4 Reconciling Different Metrics Approaches 94 4.5 Metrics for Software Quality 95 4.5.1 An Overview of Factors That Affect Quality 95 4.5.2 Measuring Quality 96 4.5.3 Defect Removal Efciency 98 4.6 Integrating Metrics Within the Software Engineering Process 98 4.6.1 Arguments for Software Metrics 99 4.6.2 Establishing a Baseline 100 4.6.3 Metrics Collection, Computation, and Evaluation 100 4.7 Managing Variation: Statistical Quality Control 100 4.8 Metrics for Small Organizations 104 4.9 Establishing a Software Metrics Program 105 4.10 Summary 107 REFERENCES 107

11. CONTENTS xi PROBLEMS AND POINTS TO PONDER 109 FURTHER READINGS AND INFORMATION SOURCES 110 CHAPTER 5 SOFTWARE PROJECT PLANNING 113 5.1 Observations on Estimating 114 5.2 Project Planning Objectives 115 5.3 Software Scope 115 5.3.1 Obtaining Information Necessary for Scope 116 5.3.2 Feasibility 117 5.3.3 A Scoping Example 118 5.4 Resources 120 5.4.1 Human Resources 121 5.4.2 Reusable Software Resources 121 5.4.3 Environmental Resources 122 5.5 Software Project Estimation 123 5.6 Decomposition Techniques 124 5.6.1 Software Sizing 124 5.6.2 Problem-Based Estimation 126 5.6.3 An Example of LOC-Based Estimation 128 5.6.4 An Example of FP-Based Estimation 129 5.6.4 Process-Based Estimation 130 5.6.5 An Example of Process-Based Estimation 131 5.7 Empirical Estimation Models 132 5.7.1 The Structure of Estimation Models 132 5.7.2 The COCOMO Model 133 5.7.3 The Software Equation 135 5.8 The Make/Buy Decision 136 5.8.1 Creating a Decision Tree 137 5.8.2 Outsourcing 138 5.9 Automated Estimation Tools 139 5.10 Summary 140 REFERENCES 140 PROBLEMS AND POINTS TO PONDER 141 FURTHER READINGS AND INFORMATION SOURCES 142 CHAPTER 6 RISK ANALYSIS AND MANAGEMENT 145 6.1 Reactive versus Proactive Risk Strategies 146 6.2 Software Risks 146 6.3 Risk Identication 148 6.3.1 Assessing Overall Project Risk 149 6.3.2 Risk Components and Drivers 149 6.4 Risk Projection 151 6.4.1 Developing a Risk Table 151 6.4.2 Assessing Risk Impact 153 6.4.3 Risk Assessment 154 6.5 Risk Renement 156 6.6 Risk Mitigation, Monitoring, and Management 156 6.7 Safety Risks and Hazards 158 6.8 The RMMM Plan 159 6.9 Summary 159 REFERENCES 160

12. CONTENTSxii PROBLEMS AND POINTS TO PONDER 161 FURTHER READINGS AND INFORMATION SOURCES 162 CHAPTER 7 PROJECT SCHEDULING AND TRACKING 165 7.1 Basic Concepts 166 7.1.1 Comments on Lateness 167 7.2.1 Basic Principles 168 7.2 The Relationship Between People and Effort 170 7.2.1 An Example 170 7.2.2 An Empirical Relationship 171 7.2.3 Effort Distribution 172 7.3 Dening a Task Set for the Software Project 172 7.3.1 Degree of Rigor 173 7.3.2 Dening Adaptation Criteria 174 7.3.3 Computing a Task Set Selector Value 175 7.3.4 Interpreting the TSS Value and Selecting the Task Set 176 7.4 Selecting Software Engineering Tasks 177 7.5 Renement of Major Tasks 178 7.6 Dening a Task Network 180 7.7 Scheduling 181 7.7.1 Timeline Charts 182 7.7.2 Tracking the Schedule 185 7.8 Earned Value Analysis 186 7.9 Error Tracking 187 7.10 The Project Plan 189 7.11 Summary 189 REFERENCES 189 PROBLEMS AND POINTS TO PONDER 190 FURTHER READINGS AND INFORMATION SOURCES 192 CHAPTER 8 SOFTWARE QUALITY ASSURANCE 193 8.1 Quality Concepts 194 8.1.1 Quality 195 8.1.2 Quality Control 196 8.1.3 Quality Assurance 196 8.1.4 Cost of Quality 196 8.2 The Quality Movement 198 8.3 Software Quality Assurance 199 8.3.1 Background Issues 200 8.3.2 SQA Activities 201 8.4 Software Reviews 202 8.4.1 Cost Impact of Software Defects 203 8.4.2 Defect Amplication and Removal 204 8.5 Formal Technical Reviews 205 8.5.1 The Review Meeting 206 8.5.2 Review Reporting and Record Keeping 207 8.5.3 Review Guidelines 207 8.6 Formal Approaches to SQA 209 8.7 Statistical Software Quality Assurance 209 8.8 Software Reliability 212 8.8.1 Measures of Reliability and Availability 212 8.8.2 Software Safety 213

13. CONTENTS xiii 8.9 Mistake-Proong for Software 214 8.10 The ISO 9000 Quality Standards 216 8.10.1 The ISO Approach to Quality Assurance Systems 217 8.10.2 The ISO 9001 Standard 217 8.11 The SQA Plan 218 8.12 Summary 219 REFERENCES 220 PROBLEMS AND POINTS TO PONDER 221 FURTHER READINGS AND INFORMATION SOURCES 222 CHAPTER 9 SOFTWARE CONFIGURATION MANAGEMENT 225 9.1 Software Conguration Management 226 9.1.1 Baselines 227 9.1.2 Software Conguration Items 228 9.2 The SCM Process 230 9.3 Identication of Objects in the Software Conguration 230 9.4 Version Control 232 9.5 Change Control 234 9.6 Conguration Audit 237 9.7 Status Reporting 237 9.8 SCM Standards 238 9.9 Summary 238 REFERENCES 239 PROBLEMS AND POINTS TO PONDER 239 FURTHER READINGS AND INFORMATION SOURCES 240 PART THREECONVENTIONAL METHODS FOR SOFTWARE ENGINEERING 243 CHAPTER 10 SYSTEM ENGINEERING 245 10.1 Computer-Based Systems 246 10.2 The System Engineering Hierarchy 248 10.2.1 System Modeling 249 10.2.2 System Simulation 251 10.3 Business Process Engineering: An Overview 251 10.4 Product Engineering: An Overview 254 10.5 Requirements Engineering 256 10.5.1 Requirements Elicitation 256 10.5.2 Requirements Analysis and Negotiation 258 10.5.3 Requirements Specication 259 10.5.4 System Modeling 259 10.5.5 Requirements Validation 260 10.5.6 Requirements Management 261 10.6 System Modeling 262 10.7 Summary 265 REFERENCES 267 PROBLEMS AND POINTS TO PONDER 267 FURTHER READINGS AND INFORMATION SOURCES 269

14. CONTENTSxiv CHAPTER 11 ANALYSIS CONCEPTS AND PRINCIPLES 271 11.1 Requirements Analysis 272 11.2 Requirements Elicitation for Software 274 11.2.1 Initiating the Process 274 11.2.2 Facilitated Application Specication Techniques 275 11.2.3 Quality Function Deployment 279 11.2.4 Use-Cases 280 11.3 Analysis Principles 282 11.3.1 The Information Domain 283 11.3.2 Modeling 285 11.3.3 Partitioning 286 11.3.4 Essential and Implementation Views 288 11.4 Software Prototyping 289 11.4.1 Selecting the Prototyping Approach 289 11.4.2 Prototyping Methods and Tools 290 11.5 Specication 291 11.5.1 Specication Principles 291 11.5.2 Representation 292 11.5.3 The Software Requirements Specication 293 11.6 Specication Review 294 11.7 Summary 294 REFERENCES 295 PROBLEMS AND POINTS TO PONDER 296 FURTHER READINGS AND INFORMATION SOURCES 297 CHAPTER 12 ANALYSIS MODELING 299 12.1 A Brief History 300 12.2 The Elements of the Analysis Model 301 12.3 Data Modeling 302 12.3.1 Data Objects, Attributes, and Relationships 302 12.3.2 Cardinality and Modality 305 12.3.3 Entity/Relationship Diagrams 307 12.4 Functional Modeling and Information Flow 309 12.4.1 Data Flow Diagrams 311 12.4.2 Extensions for Real-Time Systems 312 12.4.3 Ward and Mellor Extensions 312 12.4.4 Hatley and Pirbhai Extensions 315 12.5 Behavioral Modeling 317 12.6 The Mechanics of Structured Analysis 319 12.6.1 Creating an Entity/Relationship Diagram 319 12.6.2 Creating a Data Flow Model 321 12.6.3 Creating a Control Flow Model 324 12.6.4 The Control Specication 325 12.6.5 The Process Specication 327 12.7 The Data Dictionary 328 12.8 Other Classical Analysis Methods 330 12.9 Summary 331 REFERENCES 331 PROBLEMS AND POINTS TO PONDER 332 FURTHER READINGS AND INFORMATION SOURCES 334

15. CONTENTS xv CHAPTER 13 DESIGN CONCEPTS AND PRINCIPLES 335 13.1 Software Design and Software Engineering 336 13.2 The Design Process 338 13.2.1 Design and Software Quality 338 13.2.2 The Evolution of Software Design 339 13.3 Design Principles 340 13.4 Design Concepts 341 13.4.1 Abstraction 342 13.4.2 Renement 343 13.4.3 Modularity 343 13.4.4 Software Architecture 346 13.4.5 Control Hierarchy 347 13.4.6 Structural Partitioning 348 13.4.7 Data Structure 349 13.4.8 Software Procedure 351 13.4.9 Information Hiding 351 13.5 Effective Modular Design 352 13.5.1 Functional Independence 352 13.5.2 Cohesion 353 13.5.3 Coupling 354 13.6 Design Heuristics for Effective Modularity 355 13.7 The Design Model 357 13.8 Design Documentation 358 13.9 Summary 359 REFERENCES 359 PROBLEMS AND POINTS TO PONDER 361 FURTHER READINGS AND INFORMATION SOURCES 362 CHAPTER 14 ARCHITECTURAL DESIGN 365 14.1 Software Architecture 366 14.1.1 What Is Architecture? 366 14.1.2 Why Is Architecture Important? 367 14.2 Data Design 368 14.2.1 Data Modeling, Data Structures, Databases, and the Data Warehouse 368 14.2.2 Data Design at the Component Level 369 14.3 Architectural Styles 371 14.3.1 A Brief Taxonomy of Styles and Patterns 371 14.3.2 Organization and Renement 374 14.4 Analyzing Alternative Architectural Designs 375 14.4.1 An Architecture Trade-off Analysis Method 375 14.4.2 Quantitative Guidance for Architectural Design 376 14.4.3 Architectural Complexity 378 14.5 Mapping Requirements into a Software Architecture 378 14.5.1 Transform Flow 379 14.5.2 Transaction Flow 380 14.6 Transform Mapping 380 14.6.1 An Example 380 14.6.2 Design Steps 381 14.7 Transaction Mapping 389 14.7.1 An Example 390 14.7.2 Design Steps 390

16. CONTENTSxvi 14.8 Rening the Architectural Design 394 14.9 Summary 395 REFERENCES 396 PROBLEMS AND POINTS TO PONDER 397 FURTHER READINGS AND INFORMATION SOURCES 399 CHAPTER 15 USER INTERFACE DESIGN 401 15.1 The Golden Rules 402 15.1.1 Place the User in Control 402 15.1.2 Reduce the Users Memory Load 404 15.1.3 Make the Interface Consistent 404 15.2 User Interface Design 405 15.2.1 Interface Design Models 405 15.2.2 The User Interface Design Process 407 15.3 Task Analysis and Modeling 408 15.4 Interface Design Activities 410 15.4.1 Dening Interface Objects and Actions 410 15.4.2 Design Issues 413 15.5 Implementation Tools 415 15.6 Design Evaluation 416 15.7 Summary 418 REFERENCES 418 PROBLEMS AND POINTS TO PONDER 419 FURTHER READINGS AND INFORMATION SOURCES 420 CHAPTER 16 COMPONENT-LEVEL DESIGN 423 16.1 Structured Programming 424 16.1.1 Graphical Design Notation 425 16.1.2 Tabular Design Notation 427 16.1.3 Program Design Language 429 16.1.4 A PDL Example 430 16.2 Comparison of Design Notation 432 16.3 Summary 433 REFERENCES 433 PROBLEMS AND POINTS TO PONDER 434 FURTHER READINGS AND INFORMATION SOURCES 435 CHAPTER 17 SOFTWARE TESTING TECHNIQUES 437 17.1 Software Testing Fundamentals 438 17.1.1 Testing Objectives 439 17.1.2 Testing Principles 439 17.1.3 Testability 440 17.2 Test Case Design 443 17.3 White-Box Testing 444 17.4 Basis Path Testing 445 17.4.1 Flow Graph Notation 445 17.4.2 Cyclomatic Complexity 446 17.4.3 Deriving Test Cases 449 17.4.4 Graph Matrices 452 17.5 Control Structure Testing 454 17.5.1 Condition Testing 454

17. CONTENTS xvii 17.5.2 Data Flow Testing 456 17.5.3 Loop Testing 458 17.6 Black-Box Testing 459 17.6.1 Graph-Based Testing Methods 460 17.6.2 Equivalence Partitioning 463 17.6.3 Boundary Value Analysis 465 17.6.4 Comparison Testing 465 17.6.5 Orthogonal Array Testing 466 17.7 Testing for Specialized Environments, Architectures, and Applications 468 17.7.1 Testing GUIs 469 17.7.2 Testing of Client/Server Architectures 469 17.7.3 Testing Documentation and Help Facilities 469 17.7.4 Testing for Real-Time Systems 470 17.8 Summary 472 REFERENCES 473 PROBLEMS AND POINTS TO PONDER 474 FURTHER READINGS AND INFORMATION SOURCES 475 CHAPTER 18 SOFTWARE TESTING STRATEGIES 477 18.1 A Strategic Approach to Software Testing 478 18.1.1 Verication and Validation 479 18.1.2 Organizing for Software Testing 479 18.1.3 A Software Testing Strategy 480 18.1.4 Criteria for Completion of Testing 482 18.2 Strategic Issues 484 18.3 Unit Testing 485 18.3.1 Unit Test Considerations 485 18.3.2 Unit Test Procedures 487 18.4 Integration Testing 488 18.4.1 Top-down Integration 488 18.4.2 Bottom-up Integration 490 18.4.3 Regression Testing 491 18.4.4 Smoke Testing 492 18.4.5 Comments on Integration Testing 493 18.4.6 Integration Test Documentation 494 18.5 Validation Testing 495 18.5.1 Validation Test Criteria 495 18.5.2 Conguration Review 496 18.5.3 Alpha and Beta Testing 496 18.6 System Testing 496 18.6.1 Recovery Testing 497 18.6.2 Security Testing 497 18.6.3 Stress Testing 498 18.6.4 Performance Testing 498 18.7 The Art of Debugging 499 18.7.1 The Debugging Process 499 18.7.2 Psychological Considerations 500 18.7.3 Debugging Approaches 501 18.8 Summary 502 REFERENCES 503 PROBLEMS AND POINTS TO PONDER 504 FURTHER READINGS AND INFORMATION SOURCES 505

18. CONTENTSxviii CHAPTER 19 TECHNICAL METRICS FOR SOFTWARE 507 19.1 Software Quality 508 19.1.1 McCalls Quality Factors 509 19.1.2 FURPS 511 19.1.3 ISO 9126 Quality Factors 513 19.1.4 The Transition to a Quantitative View 513 19.2 A Framework for Technical Software Metrics 514 19.2.1 The Challenge of Technical Metrics 514 19.2.2 Measurement Principles 515 19.2.3 The Attributes of Effective Software Metrics 516 19.3 Metrics for the Analysis Model 517 19.3.1 Function-Based Metrics 518 19.3.2 The Bang Metric 520 19.3.3 Metrics for Specication Quality 522 19.4 Metrics for the Design Model 523 19.4.1 Architectural Design Metrics 523 19.4.2 Component-Level Design Metrics 526 19.4.3 Interface Design Metrics 530 19.5 Metrics for Source Code 531 19.6 Metrics for Testing 532 19.7 Metrics for Maintenance 533 19.8 Summary 534 REFERENCES 534 PROBLEMS AND POINTS TO PONDER 536 FURTHER READING AND OTHER INFORMATION SOURCES 537 PART FOUROBJECT-ORIENTED SOFTWARE ENGINEERING 539 CHAPTER 20 OBJECT-ORIENTED CONCEPTS AND PRINCIPLES 541 20.1 The Object-Oriented Paradigm 542 20.2 Object-Oriented Concepts 544 20.2.1 Classes and Objects 546 20.2.2 Attributes 547 20.2.3 Operations, Methods, and Services 548 20.2.4 Messages 548 20.2.5 Encapsulation, Inheritance, and Polymorphism 550 20.3 Identifying the Elements of an Object Model 553 20.3.1 Identifying Classes and Objects 553 20.3.2 Specifying Attributes 557 20.3.3 Dening Operations 558 20.3.4 Finalizing the Object Denition 559 20.4 Management of Object-Oriented Software Projects 560 20.4.1 The Common Process Framework for OO 560 20.4.2 OO Project Metrics and Estimation 562 20.4.3 An OO Estimating and Scheduling Approach 564 20.4.4 Tracking Progress for an OO Project 565 20.5 Summary 566 REFERENCES 566 PROBLEMS AND POINTS TO PONDER 567 FURTHER READINGS AND INFORMATION SOURCES 568

19. CONTENTS xix CHAPTER 21 OBJECT-ORIENTED ANALYSIS 571 21.1 Object-Oriented Analysis 572 21.1.1 Conventional vs. OO Approaches 572 21.1.2 The OOA Landscape 573 21.1.3 A Unied Approach to OOA 575 21.2 Domain Analysis 576 21.2.1 Reuse and Domain Analysis 577 21.2.2 The Domain Analysis Process 577 21.3 Generic Components of the OO Analysis Model 579 21.4 The OOA Process 581 21.4.1 Use-Cases 581 21.4.2 Class-Responsibility-Collaborator Modeling 582 21.4.3 Dening Structures and Hierarchies 588 21.4.4 Dening Subjects and Subsystems 590 21.5 The Object-Relationship Model 591 21.6 The Object-Behavior Model 594 21.6.1 Event Identication with Use-Cases 594 21.6.2 State Representations 595 21.7 Summary 598 REFERENCES 599 PROBLEMS AND POINTS TO PONDER 600 FURTHER READINGS AND INFORMATION SOURCES 601 CHAPTER 22 OBJECT-ORIENTED DESIGN 603 22.1 Design for Object-Oriented Systems 604 22.1.1 Conventional vs. OO Approaches 605 22.1.2 Design Issues 607 22.1.3 The OOD Landscape 608 22.1.4 A Unied Approach to OOD 610 22.2 The System Design Process 611 22.2.1 Partitioning the Analysis Model 612 22.2.2 Concurrency and Subsystem Allocation 613 22.2.3 The Task Management Component 614 22.2.4 The User Interface Component 615 22.2.5 The Data Management Component 615 22.2.6 The Resource Management Component 616 22.2.7 Intersubsystem Communication 616 22.3 The Object Design Process 618 22.3.1 Object Descriptions 618 22.3.2 Designing Algorithms and Data Structures 619 22.3.3 Program Components and Interfaces 621 22.4 Design Patterns 624 22.4.1 Describing a Design Pattern 624 22.4.2 Using Patterns in Design 625 22.5 Object-Oriented Programming 625 22.6 Summary 626 REFERENCES 627 PROBLEMS AND POINTS TO PONDER 628 FURTHER READINGS AND INFORMATION SOURCES 629

20. CONTENTSxx CHAPTER 23 OBJECT-ORIENTED TESTING 631 23.1 Broadening the View of Testing 632 23.2 Testing OOA and OOD Models 633 23.2.1 Correctness of OOA and OOD Models 633 23.2.2 Consistency of OOA and OOD Models 634 23.3 Object-Oriented Testing Strategies 636 23.3.1 Unit Testing in the OO Context 636 23.3.2 Integration Testing in the OO Context 637 23.3.3 Validation Testing in an OO Context 637 23.4 Test Case Design for OO Software 637 23.4.1 The Test Case Design Implications of OO Concepts 638 23.4.2 Applicability of Conventional Test Case Design Methods 638 23.4.3 Fault-Based Testing 639 23.4.4 The Impact of OO Programming on Testing 640 23.4.5 Test Cases and the Class Hierarchy 641 23.4.6 Scenario-Based Test Design 641 23.4.7 Testing Surface Structure and Deep Structure 643 23.5 Testing Methods Applicable at the Class Level 644 23.5.1 Random Testing for OO Classes 644 23.5.2 Partition Testing at the Class Level 644 23.6 Interclass Test Case Design 645 23.6.1 Multiple Class Testing 645 23.6.2 Tests Derived from Behavior Models 647 23.7 Summary 648 REFERENCES 649 PROBLEMS AND POINTS TO PONDER 649 FURTHER READINGS AND INFORMATION SOURCES 650 CHAPTER 24 TECHNICAL METRICS FOR OBJECT-ORIENTED SYSTEMS 653 24.1 The Intent of Object-Oriented Metrics 654 24.2 The Distinguishing Characteristics of Object-Oriented Metrics 654 24.2.1 Localization 655 24.2.2 Encapsulation 655 24.2.3 Information Hiding 655 24.2.4 Inheritance 656 24.2.5 Abstraction 656 24.3 Metrics for the OO Design Model 656 24.4 Class-Oriented Metrics 658 24.4.1 The CK Metrics Suite 658 24.4.2 Metrics Proposed by Lorenz and Kidd 661 24.4.3 The MOOD Metrics Suite 662 24.5 Operation-Oriented Metrics 664 24.6 Metrics for Object-Oriented Testing 664 24.7 Metrics for Object-Oriented Projects 665 24.8 Summary 666 REFERENCES 667 PROBLEMS AND POINTS TO PONDER 668 FURTHER READINGS AND INFORMATION SOURCES 669

21. CONTENTS xxi PART FIVEADVANCED TOPICS IN SOFTWARE ENGINEERING 671 CHAPTER 25 FORMAL METHODS 673 25.1 Basic Concepts 674 25.1.1 Deciencies of Less Formal Approaches 675 25.1.2 Mathematics in Software Development 676 25.1.3 Formal Methods Concepts 677 25.2 Mathematical Preliminaries 682 25.2.1 Sets and Constructive Specication 683 25.2.2 Set Operators 684 25.2.3 Logic Operators 686 25.2.4 Sequences 686 25.3 Applying Mathematical Notation for Formal Specication 687 25.4 Formal Specication Languages 689 25.5 Using Z to Represent an Example Software Component 690 25.6 The Ten Commandments of Formal Methods 693 25.7 Formal MethodsThe Road Ahead 694 25.8 Summary 695 REFERENCES 695 PROBLEMS AND POINTS TO PONDER 696 FURTHER READINGS AND INFORMATION SOURCES 697 CHAPTER 26 CLEANROOM SOFTWARE ENGINEERING 699 26.1 The Cleanroom Approach 700 26.1.1 The Cleanroom Strategy 701 26.1.2 What Makes Cleanroom Different? 703 26.2 Functional Specication 703 26.2.1 Black-Box Specication 705 26.2.2 State-Box Specication 705 26.2.3 Clear-Box Specication 706 26.3 Cleanroom Design 706 26.3.1 Design Renement and Verication 707 26.3.2 Advantages of Design Verication 710 26.4 Cleanroom Testing 712 26.4.1 Statistical Use Testing 712 26.4.2 Certication 714 26.5 Summary 714 REFERENCES 715 PROBLEMS AND POINTS TO PONDER 716 FURTHER READINGS AND INFORMATION SOURCES 717 CHAPTER 27 COMPONENT-BASED SOFTWARE ENGINEERING 721 27.1 Engineering of Component-Based Systems 722 27.2 The CBSE Process 724 27.3 Domain Engineering 725 27.3.1 The Domain Analysis Process 726 27.3.2 Characterization Functions 727 27.3.3 Structural Modeling and Structure Points 728 27.4 Component-Based Development 730 27.4.1 Component Qualication, Adaptation, and Composition 730

22. CONTENTSxxii 27.4 2 Component Engineering 734 27.4.3 Analysis and Design for Reuse 734 27.5 Classifying and Retrieving Components 735 27.5.1 Describing Reusable Components 736 27.5.2 The Reuse Environment 738 27.6 Economics of CBSE 739 27.6.1 Impact on Quality, Productivity, and Cost 739 27.6.2 Cost Analysis Using Structure Points 741 27.6.3 Reuse Metrics 741 27.7 Summary 742 REFERENCES 743 PROBLEMS AND POINTS TO PONDER 744 FURTHER READINGS AND INFORMATION SOURCES 745 CHAPTER 28 CLIENT/SERVER SOFTWARE ENGINEERING 747 28.1 The Structure of Client/Server Systems 748 28.1.1 Software Components for c/s Systems 750 28.1.2 The Distribution of Software Components 750 28.1.3 Guidelines for Distributing Application Subsystems 752 28.1.4 Linking c/s Software Subsystems 753 28.1.5 Middleware and Object Request Broker Architectures 753 28.2 Software Engineering for c/s Systems 755 28.3 Analysis Modeling Issues 755 28.4 Design for c/s Systems 755 28.4.1 Architectural Design for Client/Server Systems 756 28.4.2 Conventional Design Approaches for Application Software 757 28.4.3 Database Design 758 28.4.4 An Overview of a Design Approach 759 28.4.5 Process Design Iteration 761 28.5 Testing Issues 761 28.5.1 Overall c/s Testing Strategy 762 28.5.2 c/s Testing Tactics 763 28.6 Summary 764 REFERENCES 764 PROBLEMS AND POINTS TO PONDER 765 FURTHER READINGS AND INFORMATION SOURCES 766 CHAPTER 29 WEB ENGINEERING 769 29.1 The Attributes of Web-Based Applications 771 29.1.1 Quality Attributes 773 29.1.2 The Technologies 773 29.2 The WebE Process 774 29.3 A Framework for WebE 775 29.4 Formulating/Analyzing Web-Based Systems 776 29.4.1 Formulation 776 29.4.2 Analysis 778 29.5 Design for Web-Based Applications 779 29.5.1 Architectural Design 780 29.5.2 Navigation Design 783 29.5.3 Interface Design 785

23. CONTENTS xxiii 29.6 Testing Web-Based Applications 786 29.7 Management Issues 787 29.7.1 The WebE Team 788 29.7.2 Project Management 789 29.7.3 SCM Issues for WebE 792 29.8 Summary 794 REFERENCES 795 PROBLEMS AND POINTS TO PONDER 796 FURTHER READINGS AND INFORMATION SOURCES 797 CHAPTER 30 REENGINEERING 799 30.1 Business Process Reengineering 800 30.1.1 Business Processes 800 30.1.2 Principles of Business Process Reengineering 801 30.1.3 A BPR Model 802 30.1.4 Words of Warning 804 30.2 Software Reengineering 804 30.2.1 Software Maintenance 804 30.2.2 A Software Reengineering Process Model 805 30.3 Reverse Engineering 809 30.3.1 Reverse Engineering to Understand Processing 810 30.3.2 Reverse Engineering to Understand Data 811 30.3.3 Reverse Engineering User Interfaces 812 30.4 Restructuring 813 30.4.1 Code Restructuring 814 30.4.2 Data Restructuring 814 30.5 Forward Engineering 814 30.5.1 Forward Engineering for Client/Server Architectures 816 30.5.2 Forward Engineering for Object-Oriented Architectures 817 30.5.3 Forward Engineering User Interfaces 818 30.6 The Economics of Reengineering 819 30.7 Summary 820 REFERENCES 820 PROBLEMS AND POINTS TO PONDER 822 FURTHER READINGS AND INFORMATION SOURCES 823 CHAPTER 31 COMPUTER-AIDED SOFTWARE ENGINEERING 825 31.1 What is CASE? 826 31.2 Building Blocks for CASE 826 31.3 A Taxonomy of CASE Tools 828 31.4 Integrated CASE Environments 833 31.5 The Integration Architecture 834 31.6 The CASE Repository 836 31.6.1 The Role of the Repository in I-CASE 836 31.6.2 Features and Content 837 31.7 Summary 841 REFERENCES 842 PROBLEMS AND POINTS TO PONDER 842 FURTHER READINGS AND INFORMATION SOURCES 843

24. CONTENTSxxiv CHAPTER 32 THE ROAD AHEAD 845 32.1 The Importance of SoftwareRevisited 846 32.2 The Scope of Change 847 32.3 People and the Way They Build Systems 847 32.4 The "New" Software Engineering Process 848 32.5 New Modes for Representing Information 849 32.6 Technology as a Driver 851 32.7 A Concluding Comment 852 REFERENCES 853 PROBLEMS AND POINTS TO PONDER 853 FURTHER READINGS AND INFORMATION SOURCES 853

25. PREFACE xxv When a computer software succeedswhen it meets the needs of the people who use it, when it performs awlessly over a long period of time, when it is easy to modify and even easier to useit can and does change things for the better. But when software failswhen its users are dissatised, when it is error prone, when it is difcult to change and even harder to usebad 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. In the 20 years since the rst edition of this book was written, 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 applications. Although managers and practitioners alike recognize the need for a more disci- plined 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 the most advanced technologies of the day. 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. Atti- tudes have changed, progress has been made, but much remains to be done before the discipline reaches full maturity. The fth edition of Software Engineering: A Practitioner's Approach is intended to serve as a guide to a maturing engineering discipline. The fth edition, like the four editions that preceded it, 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 rst year graduate level. The format and style of the fth edition have undergone signicant change, making the presentation more reader-friendly and the content more easily accessible. The fth edition is considerably more than a simple update. The book has been revised to accommodate the dramatic growth in the eld and to emphasize new and important software engineering practices. In addition, a comprehensive Web site has been developed to complement the content of the book. The Web site, which I call

26. PREFACExxvi SepaWeb, can be found at http://www.mhhe.com/pressman. Designed to be used in conjunction with the fth edition of Software Engineering: A Practitioner's Approach, SepaWeb provides a broad array of software engineering resources that will benet instructors, students, and industry professionals. Like all Web sites, SepaWeb will evolve over time, but the following major content areas will always be present: (1) a broad array of instructor resources including a comprehensive on-line Instructors Guide and supplementary teaching materials (e.g., slide presentations to supplement lectures, video-based instructional aids); (2) a wide variety of student resources including an extensive on-line learning center (encompassing study guides, Web-based resources, and self-tests), an evolving collection of tiny tools, a case study, and additional supplementary content; and (3) a detailed collection of professional resources including 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. In addition, Sepa- Web will contain other goodies that are currently in development. The 32 chapters of the fth edition have been organized into ve parts. This has been done to compartmentalize topics and assist instructors who may not have the time to complete the entire book in one term. Part One, The Product and the Process, presents an introduction to the software engineering milieu. It is intended to introduce the subject matter, and more important, to present concepts that will be necessary for later chapters. Part Two, Managing Software Projects, presents topics that are relevant to those who plan, manage, and control a software development project. Part Three, Conventional Methods for Software Engineering, presents the classical analysis, design, and testing methods that some view as the conventional school of software engineering. Part Four, Object-Oriented Software Engineering, presents object-oriented methods across the entire software engineering process, including analysis, design, and testing. Part Five, Advanced Software Engineering Topics, presents dedicated chapters that address formal methods, cleanroom software engineering, component-based software engineering, client/server software engineering, Web engineering, reengineering, and CASE. The ve-part organization of the fth 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 ve parts. For example, a "design course" might emphasize only Part Three or Part Four; a "methods course" might present selected chapters in Parts Three, Four, and Five. A "management course" would stress Parts One and Two. By organizing the fth edition in this way, I attempted to provide an instructor with a number of teaching options. SepaWeb can and should be used to supplement the content that is chosen from the book. An Instructor's Guide for Software Engineering: A Practitioner's Approach is available from SepaWeb. The Instructor's Guide presents suggestions for conducting var-

27. PREFACE xxvii ious 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 teaching aids. A comprehensive video curriculum, Essential Software Engineering, is available to complement this book. The video curriculum has been designed for industry training and has been modularized to enable individual software engineering topics to be presented on an as-needed, when-needed basis. Further information on the video can be obtained by mailing the request card at the back of this book.1 My work on the ve editions of Software Engineering: A Practitioners 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. For this reason, my thanks to the many authors of books, papers, and arti- cles as well as a new generation of contributors to electronic media (newsgroups, e- newsletters, and the World Wide Web) who have provided me with additional insight, ideas, and commentary over the past 20 years. Many have been referenced within the pages of each chapter. All deserve credit for their contribution to this rapidly evolving field. I also wish to thank the reviewers of the fifth edition: Donald H. Kraft, Louisiana State University; Panos E. Livadas, University of Florida; Joseph Lambert, Pennsylvania State University; Kenneth L. Modesitt, University of MichiganDear- born; and, James Purtilo, University of Maryland. Their comments and criticism have been invaluable. Special thanks and acknowledgement also go to Bruce Maxim of the University of MichiganDearborn, who assisted me in developing the Web site that accompanies this book. Bruce is responsible for much of its design and peda- gogical content. The content of the fth 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 teach me as much or more than I can 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 lled me with more pride. And nally, to Barbara, my love and thanks for encouraging still another edition of "the book." Roger S. Pressman 1 If the request card is missing, please visit the R. S. Pressman & Associates, Inc. Web site at http://www.rspa.com/ese or e-mail a request for information to [email protected].

28. xxviii USING THIS BOOK The fifth edition of Software Engineering: A Practitioners Approach (SEPA) has been redesigned to enhance your reading experience and to provide integrated links to the SEPA Web site, http://www.mhhe.com/pressman/. SepaWeb contains a wealth of useful supplementary information for readers of the book and a broad array of resources (e.g., an Instructors Guide, classroom slides, and video supplements) for instructors who have adopted SEPA for classroom use. A comprehensive video curriculum, Essential Software Engineering, is available to complement this book. The video curriculum has been designed for industry training and has been modularized to enable individual software engineering topics to be presented on an as-needed, when-needed basis. Further information on the video can be obtained by mailing the request card at the back of this book.1 Throughout the book, you will encounter marginal icons that should be interpreted in the following manner: Used to emphasize an important point in the body of the text. Practical advice from the real world of software engineering. Where can I nd the answer? ? XRef Provides an important cross reference within the book. The keypoint icon will help you to nd important points quickly. The advice icon provides prag- matic guidance that can help you make the right decision or avoid common problems while building software. The question mark icon asks common questions that are answered in the body of the text. The xref icon will point you to another part of the book where information relevant to the cur- rent discussion can be found. The quote icon presents inter- esting quotes that have rele- vance to the topic at hand. The WebRef icon provides direct pointers to important software engineering related Web sites. The SepaWeb pointer indicates that further information about the noted topic is available at the SEPA Web site. The SepaWeb.checklists icon points you to detailed checklists that will help you to assess the software engineering work youre doing and the work products you produce. The SepaWeb.documents icon points you to detailed doc- ument outlines, descriptions and examples contained within the SEPA Web site. Important words WebRef For pointers that will take you directly to Web resources A selected topic 1 If the card is missing, please visit the R.S. Pressman & Associates, Inc. Web site at http://www.rspa.com/ese, or e-mail to [email protected].

29. 1 P A R T I n this part of Software Engineering: A Practitioners Approach, youll learn about the product that is to be engineered and the process that provides a framework for the engineering technology. The following questions are addressed in the chapters that follow: What is computer software . . . really? Why do we struggle to build high-quality computer-based systems? How can we categorize application domains for computer software? What myths about software still exist? What is a software process? Is there a generic way to assess the quality of a process? What process models can be applied to software development? How do linear and iterative process models differ? What are their strengths and weaknesses? What advanced process models have been proposed for software engineering work? Once these questions are answered, youll be better prepared to understand the management and technical aspects of the engineering discipline to which the remainder of this book is dedicated. THE PRODUCT AND THE PROCESS One

30. 3 C H A P T E R K E Y C O N C E P T S application categories . . . . . . . 9 component-based assembly. . . . . . . . . 8 failure curves. . . . . 8 history . . . . . . . . . . 5 myths . . . . . . . . . . 12 reuse . . . . . . . . . . . . 9 software characteristics . . . . 6 software engineering . . . . . . 4 wear . . . . . . . . . . . . 7 T he warnings began more than a decade before the event, but no one paid much attention. With less than two years to the deadline, the media picked up the story. Then government ofcials voiced their concern, business and industry leaders committed vast sums of money, and nally, dire warnings of pending catastrophe penetrated the publics consciousness. Software, in the guise of the now-infamous Y2K bug, would fail and, as a result, stop the world as we then knew it. As we watched and wondered during the waning months of 1999, I couldnt help thinking of an unintentionally prophetic paragraph contained on the rst page of the fourth edition of this book. It stated: Computer software has become a driving force. It is the engine that drives business decision making. It serves as the basis for modern scientic investigation and engineering problem solving. It is a key factor that differentiates modern products and services. It is embedded in systems of all kinds: transportation, medical, telecommunications, military, industrial processes, entertainment, ofce products, . . . the list is almost endless. Software is virtually inescapable in a modern world. And as we move into the twenty-rst century, it will become the driver for new advances in everything from elementary education to genetic engineering. 1 THE PRODUCT What is it? Computer software is the product that software engineers design and build. It encompasses programs that execute within a computer of any size and architecture, documents that encompass hard-copy and virtual forms, and data that combine numbers and text but also includes representations of pictorial, video, and audio information. Who does it? Software engineers build it, and virtually everyone in the industrialized world uses it either directly or indirectly. Why is it important? Because it affects nearly every aspect of our lives and has become pervasive in our commerce, our culture, and our everyday activities. What are the steps? You build computer software like you build any successful product, by applying a 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 programs, documents, and data that are computer software. But from the users viewpoint, the work product is the resultant information that somehow makes the users world better. How do I ensure that Ive done it right? Read the remainder of this book, select those ideas applicable to the software that you build, and apply them to your work. Q U I C K L O O K

31. PART ONE THE PRODUCT AND THE PROCESS4 In the ve years since the fourth edition of this book was written, the role of software as the driving force has become even more obvious. A software-driven Inter- net has spawned its own $500 billion economy. In the euphoria created by the promise of a new economic paradigm, Wall Street investors gave tiny dot-com companies billion dollar valuations before these start-ups produced a dollar in sales. New software-driven industries have arisen and old ones that have not adapted to the new driving force are now threatened with extinction. The United States government has litigated against the softwares industrys largest company, just as it did in earlier eras when it moved to stop monopolistic practices in the oil and steel industries. Softwares impact on our society and culture continues to be profound. As its importance grows, the software community continually attempts to develop technologies that will make it easier, faster, and less expensive to build high-quality computer programs. Some of these technologies are targeted at a specific application domain (e.g., Web-site design and implementation); others focus on a technology domain (e.g., object-oriented systems); and still others are broad-based (e.g., operating systems such as LINUX). However, we have yet to develop a software technology that does it all, and the likelihood of one arising in the future is small. And yet, people bet their jobs, their comfort, their safety, their entertainment, their decisions, and their very lives on computer software. It better be right. This book presents a framework that can be used by those who build computer softwarepeople who must get it right. The technology encompasses a process, a set of methods, and an array of tools that we call software engineering. 1.1 THE EVOLVING ROLE OF SOFTWARE Today, software takes on a dual role. It is a product and, at the same time, the vehicle for delivering a product. As a product, it delivers the computing potential embodied by computer hardware or, more broadly, a network of computers that are accessible by local hardware. Whether it resides within a cellular phone or operates inside a mainframe computer, software is an information transformerproducing, managing, acquiring, modifying, displaying, or transmitting information that can be as simple as a single bit or as complex as a multimedia presentation. As the vehicle used to deliver the product, software acts as the basis for the control of the computer (operating systems), the communication of information (networks), and the creation and control of other programs (software tools and environments). Software delivers the most important product of our timeinformation. Software transforms personal data (e.g., an individuals nancial transactions) so that the data can be more useful in a local context; it manages business information to enhance competitiveness; it provides a gateway to worldwide information networks (e.g., Inter- net) and provides the means for acquiring information in all of its forms. The role of computer software has undergone signicant change over a time span of little more than 50 years. Dramatic improvements in hardware performance, pro- Ideas and technological discoveries are the driving engines of economic growth. The Wall Street Journal Software is both a product and a vehicle for delivering a product.

32. CHAPTER 1 THE PRODUCT found changes in computing architectures, vast increases in memory and storage capacity, and a wide variety of exotic input and output options have all precipitated more sophisticated and complex computer-based systems. Sophistication and complexity can produce dazzling results when a system succeeds, but they can also pose huge problems for those who must build complex systems. Popular books published during the 1970s and 1980s provide useful historical insight into the changing perception of computers and software and their impact on our culture. Osborne [OSB79] characterized a "new industrial revolution." Toffler [TOF80] called the advent of microelectronics part of "the third wave of change" in human history, and Naisbitt [NAI82] predicted a transformation from an industrial society to an "information society." Feigenbaum and McCorduck [FEI83] suggested that information and knowledge (controlled by computers) would be the focal point for power in the twenty-rst century, and Stoll [STO89] argued that the "electronic community" created by networks and software was the key to knowledge interchange throughout the world. As the 1990s began, Tofer [TOF90] described a "power shift" in which old power structures (governmental, educational, industrial, economic, and military) disinte- grate as computers and software lead to a "democratization of knowledge." Yourdon [YOU92] worried that U.S. companies might loose their competitive edge in software- related businesses and predicted the decline and fall of the American programmer. Hammer and Champy [HAM93] argued that information technologies were to play a pivotal role in the reengineering of the corporation. During the mid-1990s, the pervasiveness of computers and software spawned a rash of books by neo-Luddites (e.g., Resisting the Virtual Life, edited by James Brook and Iain Boal and The Future Does Not Compute by Stephen Talbot). These authors demonized the computer, empha- sizing legitimate concerns but ignoring the profound benets that have already been realized. [LEV95] During the later 1990s, Yourdon [YOU96] re-evaluated the prospects for the software professional and suggested the the rise and resurrection of the Ameri- can programmer. As the Internet grew in importance, his change of heart proved to be correct. As the twentieth century closed, the focus shifted once more, this time to the impact of the Y2K time bomb (e.g., [YOU98b], [DEJ98], [KAR99]). Although the predictions of the Y2K doomsayers were incorrect, their popular writings drove home the pervasiveness of software in our lives. Today, ubiquitous computing [NOR98] has spawned a generation of information appliances that have broadband connectivity to the Web to provide a blanket of connectedness over our homes, offices and motorways [LEV99]. Softwares role continues to expand. The lone programmer of an earlier era has been replaced by a team of software specialists, each focusing on one part of the technology required to deliver a complex application. And yet, the same questions asked of the lone programmer are being asked when modern computer-based systems are built: 5 For I dipped into the future, far as the human eye could see, Saw the vision of the world, and all the wonder that would be. Tennyson Computers make it easy to do a lot of things, but most of the things that they make it easier to do don't need to be done. Andy Rooney

33. PART ONE THE PRODUCT AND THE PROCESS6 Why does it take so long to get software nished? Why are development costs so high? Why can't we nd all the errors before we give the software to customers? Why do we continue to have difculty in measuring progress as software is being developed? These, and many other questions,1 are a manifestation of the concern about software and the manner in which it is developeda concern that has lead to the adop- tion of software engineering practice. 1.2 SOFTWARE In 1970, less than 1 percent of the public could have intelligently described what "computer software" meant. Today, most professionals and many members of the public at large feel that they understand software. But do they? A textbook description of software might take the following form: Software is (1) instructions (computer programs) that when executed provide desired function and performance, (2) data structures that enable the programs to adequately manipulate information, and (3) documents that describe the operation and use of the programs. There is no question that other, more complete denitions could be offered. But we need more than a formal denition. 1.2.1 Software Characteristics To gain an understanding of software (and ultimately an understanding of software engineering), it is important to examine the characteristics of software that make it different from other things that human beings build. When hardware is built, the human creative process (analysis, design, construction, testing) is ultimately translated into a physical form. If we build a new computer, our initial sketches, formal design drawings, and breadboarded prototype evolve into a physical product (chips, circuit boards, power supplies, etc.). Software is a logical rather than a physical system element. Therefore, software has characteristics that are considerably different than those of hardware: 1. Software is developed or engineered, it is not manufactured in the classical sense. Although some similarities exist between software development and hardware man- ufacture, the two activities are fundamentally different. In both activities, high qual- How should we dene software? ? 1 In an excellent book of essays on the software business, Tom DeMarco [DEM95] argues the coun- terpoint. He states: Instead of asking why does software cost so much? we need to begin asking What have we done to make it possible for todays software to cost so little? The answer to that question will help us continue the extraordinary level of achievement that has always distin- guished the software industry. Software is engineered, not manufactured.

34. CHAPTER 1 THE PRODUCT ity is achieved through good design, but the manufacturing phase for hardware can introduce quality problems that are nonexistent (or easily corrected) for software. Both activities are dependent on people, but the relationship between people applied and work accomplished is entirely different (see Chapter 7). Both activities require the construction of a "product" but the approaches are different. Software costs are concentrated in engineering. This means that software projects cannot be managed as if they were manufacturing projects. 2. Software doesn't "wear out." Figure 1.1 depicts failure rate as a function of time for hardware. The relationship, often called the "bathtub curve," indicates that hardware exhibits relatively high failure rates early in its life (these failures are often attributable to design or manufacturing defects); defects are corrected and the failure rate drops to a steady-state level (ideally, quite low) for some period of time. As time passes, however, the failure rate rises again as hardware components suffer from the cumulative affects of dust, vibra- tion, abuse, temperature extremes, and many other environmental maladies. Stated simply, the hardware begins to wear out. Software is not susceptible to the environmental maladies that cause hardware to wear out. In theory, therefore, the failure rate curve for software should take the form of the idealized curve shown in Figure 1.2. Undiscovered defects will cause high failure rates early in the life of a program. However, these are corrected (ideally, without intro- ducing other errors) and the curve attens as shown.The idealized curve is a gross over- simplication of actual failure models (see Chapter 8 for more information) for software. However, the implication is clearsoftware doesn't wear out. But it does deteriorate! This seeming contradiction can best be explained by considering the actual curve shown in Figure 1.2. During its life, software will undergo change (maintenance). As 7 Wear outInfant mortality Time Failurerate FIGURE 1.1 Failure curve for hardware Software doesnt wear out, but it does deteriorate.

35. PART ONE THE PRODUCT AND THE PROCESS8 changes are made, it is likely that some new defects will be introduced, causing the failure rate curve to spike as shown in Figure 1.2. Before the curve can return to the original steady-state failure rate, another change is requested, causing the curve to spike again. Slowly, the minimum failure rate level begins to risethe software is deteriorating due to change. Another aspect of wear illustrates the difference between hardware and software. When a hardware component wears out, it is replaced by a spare part. There are no software spare parts. Every software failure indicates an error in design or in the process through which design was translated into machine executable code. There- fore, software maintenance involves considerably more complexity than hardware maintenance. 3. Although the industry is moving toward component-based assembly, most software continues to be custom built. Consider the manner in which the control hardware for a computer-based product is designed and built. The design engineer draws a simple schematic of the digital circuitry, does some fundamental analysis to assure that proper function will be achieved, and then goes to the shelf where catalogs of digital components exist. Each integrated circuit (called an IC or a chip) has a part number, a dened and validated function, a well-dened interface, and a standard set of integration guidelines. After each component is selected, it can be ordered off the shelf. As an engineering discipline evolves, a collection of standard design components is created. Standard screws and off-the-shelf integrated circuits are only two of thousands of standard components that are used by mechanical and electrical engineers as they design new systems. The reusable components have been created so that the engineer can concentrate on the truly innovative elements of a design, that is, the FIGURE 1.2 Idealized and actual failure curves for software Increased failure rate due to side effects Time Failurerate Change Actual curve Idealized curve Most software continues to be custom built. Software engineering methods strive to reduce the magnitude of the spikes and the slope of the actual curve in Figure 1.2.

36. CHAPTER 1 THE PRODUCT parts of the design that represent something new. In the hardware world, component reuse is a natural part of the engineering process. In the software world, it is something that has only begun to be achieved on a broad scale. A software component should be designed and implemented so that it can be reused in many different programs. In the 1960s, we built scientic subroutine libraries that were reusable in a broad array of engineering and scientic applications. These subroutine libraries reused well-dened algorithms in an effective manner but had a limited domain of application. Today, we have extended our view of reuse to encompass not only algorithms but also data structure. Modern reusable components encap- sulate both data and the processing applied to the data, enabling the software engineer to create new applications from reusable parts. For example, today's graphical user interfaces are built using reusable components that enable the creation of graphics windows, pull-down menus, and a wide variety of interaction mechanisms. The data structure and processing detail required to build the interface are contained with a library of reusable components for interface construction. 1.2.2 Software Applications Software may be applied in any situation for which a prespecied set of procedural steps (i.e., an algorithm) has been dened (notable exceptions to this rule are expert system software and neural network software). Information content and determinacy are important factors in determining the nature of a software application. Content refers to the meaning and form of incoming and outgoing information. For example, many business applications use highly structured input data (a database) and produce formatted reports. Software that controls an automated machine (e.g., a numerical control) accepts discrete data items with limited structure and produces individual machine commands in rapid succession. Information determinacy refers to the predictability of the order and timing of information. An engineering analysis program accepts data that have a predened order, executes the analysis algorithm(s) without interruption, and produces resultant data in report or graphical format. Such applications are determinate. A multiuser operating system, on the other hand, accepts inputs that have varied content and arbi- trary timing, executes algorithms that can be interrupted by external conditions, and produces output that varies as a function of environment and time. Applications with these characteristics are indeterminate. It is somewhat difcult to develop meaningful generic categories for software applications. As software complexity grows, neat compartmentalization disappears. The following software areas indicate the breadth of potential applications: System software. System software is a collection of programs written to service other programs. Some system software (e.g., compilers, editors, and le management utilities) process complex, but determinate, information structures. Other systems applications (e.g., operating system components, drivers, telecommunications 9 XRef Software reuse is discussed in Chapter 13. Component-based software engineering is presented in Chapter 27.

37. PART ONE THE PRODUCT AND THE PROCESS10 processors) process largely indeterminate data. In either case, the system software area is characterized by heavy interaction with computer hardware; heavy usage by multiple users; concurrent operation that requires scheduling, resource sharing, and sophisticated process management; complex data structures; and multiple external interfaces. Real-time software. Software that monitors/analyzes/controls real-world events as they occur is called real time. Elements of real-time software include a data gath- ering component that collects and formats information from an external environment, an analysis component that transforms information as required by the application, a control/output component that responds to the external environment, and a monitoring component that coordinates all other components so that real-time response (typically ranging from 1 millisecond to 1 second) can be maintained. Business software. Business information processing is the largest single software application area. Discrete "systems" (e.g., payroll, accounts receivable/payable, inven- tory) have evolved into management information system (MIS) software that accesses one or more large databases containing business information. Applications in this area restructure existing data in a way that facilitates business operations or management decision making. In addition to conventional data processing application, business software applications also encompass interactive computing (e.g., point- of-sale transaction processing). Engineering and scientic software. Engineering and scientic software have been characterized by "number crunching" algorithms. Applications range from astron- omy to volcanology, from automotive stress analysis to space shuttle orbital dynam- ics, and from molecular biology to automated manufacturing. However, modern applications within the engineering/scientic area are moving away from conventional numerical algorithms. Computer-aided design, system simulation, and other interactive applications have begun to take on real-time and even system software characteristics. Embedded software. Intelligent products have become commonplace in nearly every consumer and industrial market. Embedded software resides in read-only memory and is used to control products and systems for the consumer and industrial mar- kets. Embedded software can perform very limited and esoteric functions (e.g., keypad control for a microwave oven) or provide signicant function and control capability (e.g., digital functions in an automobile such as fuel control, dashboard displays, and braking systems). Personal computer software. The personal computer software market has bur- geoned over the past two decades. Word processing, spreadsheets, computer graphics, multimedia, entertainment, database management, personal and business nancial applications, external network, and database access are only a few of hundreds of applications. Web-based software. The Web pages retrieved by a browser are software that incorporates executable instructions (e.g., CGI, HTML, Perl, or Java), and data (e.g., One of the most comprehensive libraries of shareware/freeware can be found at www.shareware.com

38. CHAPTER 1 THE PRODUCT hypertext and a variety of visual and audio formats). In essence, the network becomes a massive computer providing an almost unlimited software resource that can be accessed by anyone with a modem. Artificial intelligence software. Artificial intelligence (AI) software makes use of nonnumerical algorithms to solve complex problems that are not amenable to computation or straightforward analysis. Expert systems, also called knowledge- based systems, pattern recognition (image and voice), artificial neural networks, theorem proving, and game playing are representative of applications within this category. 1.3 SOFTWARE: A CRISIS ON THE HORIZON? Many industry observers (including this author) have characterized the problems associated with software development as a "crisis." More than a few books (e.g., [GLA97], [FLO97], [YOU98a]) have recounted the impact of some of the more spectacular software failures that have occurred over the past decade. Yet, the great successes achieved by the software industry have led many to question whether the term software crisis is still appropriate. Robert Glass, the author of a number of books on software failures, is representative of those who have had a change of heart. He states [GLA98]: I look at my failure stories and see exception reporting, spectacular failures in the midst of many successes, a cup that is [now] nearly full. It is true that software people succeed more often than they fail. It also true that the software crisis predicted 30 years ago never seemed to materialize. What we really have may be something rather different. The word crisis is dened in Webster's Dictionary as a turning point in the course of anything; decisive or crucial time, stage or event. Yet, in terms of overall software quality and the speed with which computer-based systems and products are developed, there has been no "turning point," no "decisive time," only slow, evolutionary change, punctuated by explosive technological changes in disciplines associated with software. The word crisis has another denition: "the turning point in the course of a disease, when it becomes clear whether the patient will live or die." This denition may give us a clue about the real nature of the problems that have plagued software development. What we really have might be better characterized as a chronic affliction.2 The word afiction is dened as "anything causing pain or distress." But the denition of the adjective chronic is the key to our argument: "lasting a long time or recurring often; continuing indenitely." It is far more accurate to describe the problems we have endured in the software business as a chronic afiction than a crisis. Regardless of what we call it, the set of problems that are encountered in the development of computer software is not limited to software that "doesn't function 11 2 This terminology was suggested by Professor Daniel Tiechrow of the University of Michigan in a talk presented in Geneva, Switzerland, April 1989. The most likely way for the world to be destroyed, most experts agree, is by accident. That's where we come in; we're computer professionals. We cause accidents. Nathaniel Borenstein

39. PART ONE THE PRODUCT AND THE PROCESS12 properly." Rather, the affliction encompasses problems associated with how we develop software, how we support a growing volume of existing software, and how we can expect to keep pace with a growing demand for more software. We live with this afiction to this dayin fact, the industry prospers in spite of it. And yet, things would be much better if we could nd and broadly apply a cure. 1.4 SOFTWARE MYTHS Many causes of a software afiction can be traced to a mythology that arose during the early history of software development. Unlike ancient myths that often provide human lessons well worth heeding, software myths propagated misinformation and confusion. Software myths had a number of attributes that made them insidious; for instance, they appeared to be reasonable statements of fact (sometimes containing elements of truth), they had an intuitive feel, and they were often promulgated by experienced practitioners who "knew the score." Today, most knowledgeable professionals recognize myths for what they are misleading attitudes that have caused serious problems for managers and technical people alike. However, old attitudes and habits are difcult to modify, and remnants of software myths are still believed. Management myths. Managers with software responsibility, like managers in most disciplines, are often under pressure to maintain budgets, keep schedules from slip- ping, and improve quality. Like a drowning person who grasps at a straw, a software manager often grasps at belief in a software myth, if that belief will lessen the pressure (even temporarily). Myth: We already have a book that's full of standards and procedures for building software, won't that provide my people with everything they need to know? Reality: The book of standards may very well exist, but is it used? Are software practitioners aware of its existence? Does it reect modern software engineering practice? Is it complete? Is it streamlined to improve time to delivery while still main- taining a focus on quality? In many cases, the answer to all of these questions is "no." Myth: My people have state-of-the-art software development tools, after all, we buy them the newest computers. Reality: It takes much more than the latest model mainframe, workstation, or PC to do high-quality software development. Computer-aided software engineering (CASE) tools are more important than hardware for achieving good quality and productivity, yet the majority of software developers still do not use them effectively. Myth: If we get behind schedule, we can add more programmers and catch up (sometimes called the Mongolian horde concept). Reality: Software development is not a mechanistic process like manufacturing. In the words of Brooks [BRO75]: "adding people to a late software project makes it In the absence of meaningful standards, a new industry like software comes to depend instead on folklore. Tom DeMarco

40. CHAPTER 1 THE PRODUCT later." At rst, this statement may seem counterintuitive. However, as new people are added, people who were working must spend time educating the newcomers, thereby reducing the amount of time spent on productive development effort. Peo- ple can be added but only in a planned and well-coordinated manner. Myth: If I decide to outsource3 the software project to a third party, I can just relax and let that rm build it. Reality: If an organization does not understand how to manage and control software projects internally, it will invariably struggle when it outsources software projects. Customer myths. A customer who requests computer software may be a person at the next desk, a technical group down the hall, the marketing/sales department, or an outside company that has requested software under contract. In many cases, the customer believes myths about software because software managers and practitioners do little to correct misinformation. Myths lead to false expectations (by the customer) and ultimately, dissatisfaction with the developer. Myth: A general statement of objectives is sufcient to begin writing programs we can ll in the details later. Reality: A poor up-front denition is the major cause of failed software efforts. A formal and detailed description of the information domain, function, behavior, performance, interfaces, design constraints, and validation criteria is essential. These characteristics can be determined only after thorough communication between customer and developer. Myth: Project requirements continually change, but change can be easily accommodated because software is exible. Reality: It is true that software requirements change, but the impact of change varies with the time at which it is introduced. Figure 1.3 illustrates the impact of change. If serious attention is given to up-front denition, early requests for change can be accommodated easily. The customer can review requirements and recom- mend modications with relatively little impact on cost. When changes are requested during software design, the cost impact grows rapidly. Resources have been committed and a design framework has been established. Change can cause upheaval that requires additional resources and major design modication, that is, additional cost. Changes in function, performance, interface, or other characteristics during implementation (code and test) have a severe impact on cost. Change, when requested after software is in production, can be over an order of magnitude more expensive than the same change requested earlier. 13 The Software Project Managers Network at www.spmn.com can help you dispel these and other myths. XRef The management and control of change is considered in detail in Chapter 9. 3 The term outsourcing refers to the widespread practice of contracting software development work to a third partyusually a consulting rm that specializes in building custom software for its clients. Work very hard to understand what you have to do before you start. You may not be able to develop every detail, but the more you know, the less risk you take.

41. PART ONE THE PRODUCT AND THE PROCESS14 Practitioner's myths. Myths that are still believed by software practitioners have been fostered by 50 years of programming culture. During the early days of software, programming was viewed as an art form. Old ways and attitudes die hard. Myth: Once we write the program and get it to work, our job is done. Reality: Someone once said that "the sooner you begin 'writing code', the longer it'll take you to get done." Industry data ([LIE80], [JON91], [PUT97]) indicate that between 60 and 80 percent of all effort expended on software will be expended after it is delivered to the customer for the rst time. Myth: Until I get the program "running" I have no way of assessing its quality. Reality: One of the most effective software quality assurance mechanisms can be applied from the inception of a projectthe formal technical review. Software reviews (described in Chapter 8) are a "quality lter" that have been found to be more effective than testing for nding certain classes of software defects. Myth: The only deliverable work product for a successful project is the working program. Reality: A working program is only one part of a software conguration that includes many elements. Documentation provides a foundation for successful engineering and, more important, guidance for software support. Myth: Software engineering will make us create voluminous and unnecessary documentation and will invariably slow us down. Reality: Software engineering is not about creating documents. It is about creating quality. Better quality leads to reduced rework. And reduced rework results in faster delivery times. Many software professionals recognize the fallacy of the myths just described. Regret- tably, habitual attitudes and methods foster poor management and technical practices, even when reality dictates a better approach. Recognition of software realities is the rst step toward formulation of practical solutions for software engineering. 1 Definition 1.56 Development 60100 After release Costtochange FIGURE 1.3 The impact of change Whenever you think, we dont have time for software engineering discipline, ask yourself: Will we have time to do it over again?

42. CHAPTER 1 THE PRODUCT 1.5 SUMMARY Software has become the key element in the evolution of computer-based systems and products. Over the past 50 years, software has evolved from a specialized problem solving and information analysis tool to an industry in itself. But early programming culture and history have created a set of problems that persist today. Software has become the limiting factor in the continuing evolution of computer- based systems. Software is composed of programs, data, and documents. Each of these items comprises a conguration that is created as part of the software engineering process. The intent of software engineering is to provide a framework for building software with higher quality. REFERENCES [BRO75] Brooks, F., The Mythical Man-Month, Addison-Wesley, 1975. [DEJ98] De Jager, P. et al., Countdown Y2K: Business Survival Planning for the Year 2000, Wiley, 1998. [DEM95] DeMarco, T., Why Does Software Cost So Much? Dorset House, 1995, p. 9. [FEI83] Feigenbaum, E.A. and P. McCorduck, The Fifth Generation, Addison- Wesley, 1983. [FLO97] Flowers, S., Software Failure, Management FailureAmazing Stories and Cautionary Tales, Wiley, 1997. [GLA97] Glass, R.L., Software Runaways, Prentice-Hall, 1997. [GLA98] Glass, R.L., Is There Really a Software Crisis? IEEE Software, vol. 15, no. 1, January 1998, pp. 104105. [HAM93] Hammer, M., and J. Champy, Reengineering the Corporation, HarperCollins Publishers, 1993. [JON91] Jones, C., Applied Software Measurement, McGraw-Hill, 1991. [KAR99] Karlson, E. and J. Kolber, A Basic Introduction to Y2K: How the Year 2000 Computer Crisis Affects YOU, Next Era Publications, 1999. [LEV95] Levy, S., The Luddites Are Back, Newsweek, July 12, 1995, p. 55. [LEV99] Levy, S., The New Digital Galaxy, Newsweek, May 31, 1999, p. 57. [LIE80] Lientz, B. and E. Swanson, Software Maintenance Management, Addison- Wesley, 1980. [NAI82] Naisbitt, J., Megatrends, Warner Books, 1982. [NOR98] Norman, D., The Invisible Computer, MIT Press, 1998. [OSB79] Osborne, A., Running WildThe Next Industrial Revolution, Osborne/McGraw-Hill, 1979. [PUT97] Putnam, L. and W. Myers, Industrial Strength Software, IEEE Computer Society Press, 1997. [STO89] Stoll, C., The Cuckoo's Egg, Doubleday, 1989. [TOF80] Tofer, A., The Third Wave, Morrow, 1980. 15

43. PART ONE THE PRODUCT AND THE PROCESS16 [TOF90] Tofer, A., Powershift, Bantam Publishers, 1990. [YOU92] Yourdon, E., The Decline and Fall of the American Programmer, Yourdon Press, 1992. [YOU96] Yourdon, E., The Rise and Resurrection of the American Programmer, Your- don Press, 1996. [YOU98a] Yourdon, E., Death March Projects, Prentice-Hall, 1998. [YOU98b] Yourdon, E. and J. Yourdon, Time Bomb 2000, Prentice-Hall, 1998. PROBLEMS AND POINTS TO PONDER 1.1. Software is the differentiating characteristic in many computer-based products and systems. Provide examples of two or three products and at least one system in which software, not hardware, is the differentiating element. 1.2. In the 1950s and 1960s, computer programming was an art form learned in an apprenticelike environment. How have the early days affected software development practices today? 1.3. Many authors have discussed the impact of the "information era." Provide a number of examples (both positive and negative) that indicate the impact of software on our society. Review one of the pre-1990 references in Section 1.1 and indicate where the authors predictions were right and where they were wrong. 1.4. Choose a specic application and indicate: (a) the software application category (Section 1.2.2) into which it ts; (b) the data content associated with the application; and (c) the information determinacy of the application. 1.5. As software becomes more pervasive, risks to the public (due to faulty programs) become an increasingly significant concern. Develop a realistic doomsday scenario (other than Y2K) where the failure of a computer program could do great harm (either economic or human). 1.6. Peruse the Internet newsgroup comp.risks and prepare a summary of risks to the public that have recently been discussed. An alternate source is Software Engi- neering Notes published by the ACM. 1.7. Write a paper summarizing recent advances in one of the leading edge software application areas. Potential choices include: advanced Web-based applications, virtual reality, articial neural networks, advanced human interfaces, intelligent agents. 1.8. The myths noted in Section 1.4 are slowly fading as the years pass, but others are taking their place. Attempt to add one or two new myths to each category.

44. CHAPTER 1 THE PRODUCT FURTHER READINGS AND INFORMATION SOURCES Literally thousands of books are written about computer software. The vast majority discuss programming languages or software applications, but a few discuss software itself. Pressman and Herron (Software Shock, Dorset House, 1991) presented an early discussion (directed at the layperson) of software and the way professionals build it. Negroponte's (Being Digital, Alfred A. Knopf, 1995) best-selling book provides a view of computing and its overall impact in the twenty-rst century. Books by Nor- man [NOR98] and Bergman (Information Appliances and Beyond, Academic Press/Mor- gan Kaufmann, 2000) suggest that the widespread impact of the PC will decline as information appliances and pervasive computing connect everyone in the industrialized world and almost every appliance that they own to a new Internet infrastructure. Minasi (The Software Conspiracy: Why Software Companies Put out Faulty Products, How They Can Hurt You, and What You Can Do, McGraw-Hill, 2000) argues that the modern scourge of software bugs can be eliminated and suggests ways to accom- plish this. DeMarco (Why Does Software Cost So Much? Dorset House, 1995) has produced a collection of amusing and insightful essays on software and the process through which it is developed. A wide variety of information sources on software-related topics and management is available on the Internet. An up-to-date list of World Wide Web references that are relevant to software can be found at the SEPA Web site: http://www.mhhe.com/engcs/compsci/pressman/resources/product.mhtml 17

45. 19 C H A P T E R K E Y C O N C E P T S common process framework . . . . . . 23 component-based development. . . . . 42 concurrent development. . . . . 40 evolutionary process models. . . . . . . . . . 34 formal methods . . 43 4GT . . . . . . . . . . . . 44 maintenance activities . . . . . . . 21 process maturity levels. . . . . . . . . . . 24 prototyping . . . . . 30 RAD. . . . . . . . . . . . 32 software engineering. . . . . . 20 I n a fascinating book that provides an economists view of software and software engineering, Howard Baetjer, Jr. [BAE98], comments on the software process: Because software, like all capital, is embodied knowledge, and because that knowledge is initially dispersed, tacit, latent, and incomplete in large measure, software development is a social learning process. The process is a dialogue in which the knowledge that must become the software is brought together and embodied in the software. The process provides interaction between users and designers, between users and evolving tools, and between designers and evolving tools [technology]. It is an iterative process in which the evolving tool itself serves as the medium for communication, with each new round of the dialogue eliciting more useful knowledge from the people involved. Indeed, building computer software is an iterative learning process, and the outcome, something that Baetjer would call software capital, is an embodi- ment of knowledge collected, distilled, and organized as the process is conducted. 2 THE PROCESS What is it? When you build a product or system, its important to go through a series of pre- dictable stepsa road map that helps you create a timely, high-quality result. The road map that you follow is called a software process. Who does it? Software engineers and their managers adapt the process to their needs and then follow it. In addition, the people who have requested the software play a role in the software process. Why is it important? Because it provides stability, control, and organization to an activity that can, if left uncontrolled, become quite chaotic. What are the steps? At a detailed level, the process that you adopt depends on the software youre building. One process might be appropriate for creating software for an aircraft avionics system, while an entirely different process would be indi- cated for the creation of a Web site. What is the work product? From the point of view of a software engineer, the work products are the programs, documents, and data produced as a consequence of the software engineering activities dened by the process. How do I ensure that Ive done it right? A number of software process assessment mechanisms enable organizations to determine the maturity of a software process. However, the quality, timeliness, and long-term viability of the product you build are the best indicators of the efcacy of the process that you use. Q U I C K L

Software Engineering by Roger Presmen

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Transcript of Software Engineering by Roger Presmen