Table of Contents

Series Editor Foreword xv
Foreword by Rebecca Wirfs-Brock xix
Foreword by Kent Beck xxi
Preface xxiii
Acknowledgments xxix
About the Author xxxi

Introduction 1

Part I: Coupling 3

Chapter 1: Coupling and System Design 5
What Is Coupling? 5
Magnitude of Coupling 6
Flow of Knowledge 10
Systems 10
Key Takeaways 16
Quiz 17

Chapter 2: Coupling and Complexity: Cynefin 19
What Is Complexity? 19
Cynefin 20
Comparing Cynefin Domains 26
Cynefin in Software Design 27
Cynefin Applications 31
Cynefin and Complexity 32
Key Takeaways 32
Quiz 33

Chapter 3: Coupling and Complexity: Interactions 35
Nature of Complexity 35
Complexity and System Design 36
Hierarchical Complexity 39
Degrees of Freedom 43
Complexity and Constraints 46
Coupling and Complex Interactions 47
Example: Connecting Coupling and Complexity 48
Key Takeaways 54
Quiz 54

Chapter 4: Coupling and Modularity 57
Modularity 57
Modules 59
Modularity in Software Systems 62
Modularity, Complexity, and Coupling 68
Coupling in Modularity 73
Key Takeaways 74
Quiz 74

Part II: Dimensions 77

Chapter 5: Structured Design's Module Coupling 79
Structured Design 80
Module Coupling 80
Comparison of Module Coupling Levels 94
Key Takeaways 95
Quiz 96

Chapter 6: Connascence 97
What Is Connascence? 97
Static Connascence 98
Dynamic Connascence 104
Evaluating Connascence 110
Key Takeaways 113
Quiz 114

Chapter 7: Integration Strength 117
Strength of Coupling 118
Integration Strength 121
Intrusive Coupling 122
Functional Coupling 125
Model Coupling 128
Contract Coupling 134
Integration Strength Discussion 143
Integration Strength and Asynchronous Execution 146
Key Takeaways 147
Quiz 148

Chapter 8: Distance 151
Distance and Encapsulation Boundaries 151
Additional Factors Affecting Distance 157
Distance Versus Proximity 160
Distance Versus Integration Strength 161
Key Takeaways 161
Quiz 162

Chapter 9: Volatility 165
Changes and Coupling 165
Why Software Changes 166
Evaluating Rates of Changes 169
Volatility and Integration Strength 175
Inferred Volatility 177
Key Takeaways 178
Quiz 179

Part III: Balance 181

Chapter 10: Balancing Coupling 183
Combining the Dimensions of Coupling 184
Combining Strength, Distance, and Volatility 189
Balancing Coupling on a Numeric Scale 192
Key Takeaways 198
Quiz 199

Chapter 11: Rebalancing Coupling 201
Resilient Design 201
Software Change Vectors 202
Rebalancing Coupling 205
Key Takeaways 213
Quiz 213

Chapter 12: Fractal Geometry of Software Design 215
Growth 215
Innovation 223
Fractal Geometry 228
Fractal Modularity 230
Key Takeaways 230
Quiz 231

Chapter 13: Balanced Coupling in Practice 233
Microservices 233
Architectural Patterns 239
Business Objects 245
Methods 251
Key Takeaways 256
Quiz 256

Chapter 14: Conclusion 257

Epilogue 261

Appendix A: The Ballad of Coupling 263

Appendix B: Glossary of Coupling 265

Appendix C: Answers to Quiz Questions 271

Bibliography 275
Index 279