Process for System Architecture and Requirements Engineering

Derek J. Hatley is president emeritus of System Strategies, an international consulting and training firm based in Jenison, Michigan. He previously was a Staff Engineer at Smiths Industries, Avionic Systems Division, where he was responsible for systems and software development techniques. At Smiths, he developed the requirements model, managed its first major application, developed an instructional workshop to be given internally and to customers and suppliers, and presented the technique in technical papers at numerous international professional conferences. Retired for 12 years, he now enjoys a more relaxed life-with his wife of 52 years and his grown sons and their families, which include four grandchildren. Peter Hruschka, a principal of The Atlantic Systems Guild, is based in Aachen, Germany. He is widely regarded as one of the fathers of CASE, and he helped create one of the first tools to implement the Hatley/Pirbhai real-time method. His mission: introducing better quality and higher productivity in system development as a trainer, consultant, and author. He has written more than a dozen books and numerous papers (mostly in German) on software architecture, requirements engineering, and development methods. Peter loves to travel and is often found with his wife, Monika, in some of the most scenic parts of the world, trying to hit little white balls into holes that are far too small. Imtiaz A. Pirbhai was a principal of Systems Methods, based in Seattle, Washington. During his tenure at the Boeing Commercial Airplane Co., he was responsible for the development of structured methods standards and procedures. He specialized in real-time and general systems development training, utilizing the methods his team at Boeing introduced and developed. He taught and consulted internationally, introducing the methods described in Strategies for Real-Time System Specification (Dorset House, 1987) throughout the world. At the time of his death in 1992, he had begun work on the manuscript for Process for System Architecture and Requirements Engineering, completed by his coauthors Derek Hatley and Peter Hruschka.

Foreword xvii
Preface xix
Figures and Tables xv


Part I: Concepts 1

Chapter 1: Introduction 3

1.1 Purpose and Scope 3

1.2 The System Development Process 4

1.3 Underlying Principles 4

1.2 What's in a Name? 5

1.3 Audience for and Structure of the Book 6

1.4 A Participative Case Study on the Web 7

1.5 A Caveat 8



Chapter 2: What Is a System? 9

2.1 System Characteristics 9

2.2 Views of a System 18

2.3 System Requirements 24

2.4 System Summary 40



Chapter 3: A Framework for Modeling Systems 41

3.1 A Model Framework 41

3.2 Models in General 41

3.3 Exploiting System Hierarchies 45

3.4 Exploiting the What/How Classification 49

3.5 Exploiting the Information/Material/Energy Classification 55

3.6 Layered Models: The Truth at Last! 60

3.7 Model Framework Summary 70





Chapter 4: System Development Models 72



4.1 Overview 72

4.2 Architecture Model 74

4.3 Requirements Model 112

4.4 Requirements Dictionary 162

4.5 Requirements/Architecture Relationships 170

4.6 A Note on Object Orientation 178

4.7 System Models Summary and Further Reading 180



Chapter 5: The System Development Process 181

5.1 Process, Methods, and Tools 181

5.2 The Nature of the Development Process 183

5.3 The Process and the Methods 190

5.4 Roles of the System Architect and System Engineer 200

5.5 System Development Process Summary 204



Chapter 6: Applying the Models to Development 205

6.1 Overview 205

6.2 Understanding the Generic Development Structure 206

6.3 Example: A Patient-Monitoring System 209

6.4 Configuring Software and Computer Hardware 236

6.5 Modeling the Numerous Hardware Technologies 244

6.6 Computer Hardware Layers 251

6.7 Software Layers 253

6.8 Summaries 273



Chapter 7: System Development Overview Using a Meta-Model 275

7.1 Introduction 275

7.2 A Meta-Model for Development Projects 276

7.3 An Essential Model of the Development Process 277

7.4 The Enhanced Development Model 281

7.5 The Development Architecture Context 284

7.6 Development Process Architecture 288

7.7 Development Process Task Allocation 291

7.8 Variations on the Architecture Template 291





Part II: Case Study: Groundwater Analysis System 297

Chapter 8: Initial Problem Statement 299



8.1 Overview 299

8.2 Required Capabilities 300

8.3 Required Performance 301

8.4 Required Constraints 301



Chapter 9: Modeling the Known Pieces 304

9.1 Overview 304

9.2 The Requirements Context 304

9.3 The System Timing Specification 305

9.4 The Entity Model 307

9.5 The Existing Sampling Module 311



Chapter 10: Building Upon the Known Pieces 316

10.1 Top-Level Essential Model 316

10.2 Enhancing the Essential Model 331

10.3 Architecture Context 341

10.4 Building Up from the Existing Sampling Module 343

10.5 What Do We Have, and What Is Missing? 346



Chapter 11: Filling in the Blanks 348

11.1 Introduction 348

11.2 Architecture Modules 348

11.3 Allocating the Enhanced Requirements Model 349

11.4 Enhancing the Allocated Models 357

11.5 Adding the Architecture Flows and Interconnects 362

11.6 Flow-to-Interconnect Allocations 362

11.7 Merging the Top-Down and Bottom-Up Pieces 364



Chapter 12: Completing the Models 375

12.1 Introduction 375

12.2 Accuracy Allocation 375

12.3 Timing Allocation-Concurrent Architecture Modules 376

12.4 Architecture Module Specifications 378

12.5 Architecture Interconnect Specifications 382

12.6 Requirements and Architecture Dictionaries 383



Chapter 13: Groundwater Analysis System Summary 387


13.1 Overview 387





Appendix: Changes, Improvements, and Misconceptions Since the Methods' Introduction 389


A. 1 A Learning Experience 389

A. 2 Changes and Improvements 390

A. 3 Misconceptions about the Methods 397



Glossary 401

Bibliography 419

Index 425