Early praise for Design It! Others have written about risk-driven architecture before, but only Michael Keeling uses his taste for guacamole to illustrate it. Design It! is full of pragmatism, personal experience, and useful tips. This book has something to offer anyone involved in software development, and it’s fun to read. ➤ Eltjo Poort CGI, recipient of the Linda Northrop Software Architecture Award Of the numerous books that talk about software architecture, there are a select few that are really, really good. This book runs the complexity of software archi- tecture through the real world of software development and distills it into real, understandable concepts that can be applied to everyday software engineering practices. In Design It!, Michael gives you his recipes for applying these concepts, providing pragmatic guidance for success in a very tough discipline. ➤ Will Chaparro Software Development Manager, IBM Watson What I like most about Michael’s style is that it is inclusive: everyone on the team should become a better architect. His book gives us hands-on ways to achieve this by collecting many great ideas and tools that arose from the community. This book is for everyone who wants to build better software together. ➤ Thijmen de Gooijer IT Architect, Kommuninvest Sweden This book covers the essentials of design and software architecture that all devel- opment teams need to know. It is definitely going on the recommended reading list for all my teams and anyone we bring on board! ➤ Jørn Ølmheim Leading Advisor Software Architecture, Statoil ASA What sets Design It! apart for me is its fresh perspective—that the technical un- dertaking of building software is an intensely social activity. Michael manages to uniquely fuse the mechanics of software architecture together with the chemistry of design thinking. You’ll learn to move from architecture viewpoints into design mindsets and from managing architecture life cycles into telling architecture sto- ries. This is a must-have reference book on modern software architecting. ➤ Amine Chigani Chief Architect, GE Digital This book is timely, valuable, accessible, and excellent. It is a clear, informed, and practical guide to the principles and practice of software architecture, for the aspiring architect as well as the established practitioner who wants to deepen and refresh his or her skills. Michael Keeling takes the reader on a clear and re- sults-oriented journey, from the fundamentals of the field to the state of the art. ➤ Eoin Woods CTO of Endava, editor of IEEE Software’s Pragmatic Architect column, and author of Software Systems Architecture Invaluable for growing your career and your team! The perfect balance between design theory and practical activities. ➤ Joseph Kramer Software Engineering Manager, IBM Design It! From Programmer to Software Architect Michael Keeling The Pragmatic Bookshelf Raleigh, North Carolina Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and The Pragmatic Programmers, LLC was aware of a trademark claim, the designations have been printed in initial capital letters or in all capitals. The Pragmatic Starter Kit, The Pragmatic Programmer, Pragmatic Programming, Pragmatic Bookshelf, PragProg and the linking g device are trade- marks of The Pragmatic Programmers, LLC. Every precaution was taken in the preparation of this book. However, the publisher assumes no responsibility for errors or omissions, or for damages that may result from the use of information (including program listings) contained herein. Our Pragmatic books, screencasts, and audio books can help you and your team create better software and have more fun. Visit us at https://pragprog.com. The team that produced this book includes: Publisher: Andy Hunt VP of Operations: Janet Furlow Development Editor: Susannah Davidson Pfalzer Indexing: Potomac Indexing, LLC Copy Editor: Liz Welch Layout: Gilson Graphics For sales, volume licensing, and support, please contact [email protected]. For international rights, please contact [email protected]. Copyright © 2017 The Pragmatic Programmers, LLC. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form, or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior consent of the publisher. Printed in the United States of America. ISBN-13: 978-1-68050-209-1 Encoded using the finest acid-free high-entropy binary digits. Book version: P1.0—October 2017 Contents Acknowledgments . . . . . . . . . . . xi Foreword . . . . . . . . . . . . . xiii Welcome! . . . . . . . . . . . . . xv Part I — Introducing Software Architecture 1. Become a Software Architect . . . . . . . . . 3 What Software Architects Do 3 What Is Software Architecture? 7 Become an Architect for Your Team 11 Build Amazing Software 12 Case Study: Project Lionheart 14 Next Up 14 2. Design Thinking Fundamentals . . . . . . . . 15 The Four Principles of Design Thinking 15 Adopt a Design Mindset 18 Think, Do, Check 21 Next Up 24 Part II — Architecture Design Fundamentals 3. Devise a Design Strategy . . . . . . . . . . 27 Find a Design That Satisfices 27 Decide How Much to Design Up Front 29 Let Risk Be Your Guide 32 Create a Design Plan 36 Project Lionheart: The Story So Far… 38 Next Up 38 Contents • vi 4. Empathize with Stakeholders . . . . . . . . 39 Talk to the Right People 39 Create a Stakeholder Map 41 Discover the Business Goals 43 Project Lionheart: The Story So Far… 46 Next Up 47 5. Dig for Architecturally Significant Requirements . . . . 49 Limit Design Options with Constraints 49 Define the Quality Attributes 51 Look for Classes of Functional Requirements 56 Find Out What Else Influences the Architecture 58 Dig for the Information You Need 59 Build an ASR Workbook 60 Project Lionheart: The Story So Far… 62 Next Up 62 6. Choose an Architecture (Before It Chooses You) . . . . 63 Diverge to See Options, Converge to Decide 63 Accept Constraints 66 Promote Desired Quality Attributes 68 Assign Functional Responsibilities to Elements 73 Design for Change 75 Project Lionheart: The Story So Far… 77 Next Up 77 7. Create a Foundation with Patterns . . . . . . . 79 What Is an Architecture Pattern? 79 Layers Pattern 80 Ports and Adapters Pattern 82 Pipe-and-Filter Pattern 84 Service-Oriented Architecture Pattern 86 Publish-Subscribe Pattern 88 Shared-Data Pattern 90 Multi-Tier Pattern 92 Center of Competence Pattern 93 Open Source Contribution Pattern 95 Big Ball of Mud Pattern 96 Discover New Patterns 96 Project Lionheart: The Story So Far… 97 Next Up 98 Contents • vii 8. Manage Complexity with Meaningful Models . . . . . 99 Reason About the Architecture 99 Design the Meta-Model 101 Build Models into the Code 107 Project Lionheart: The Story So Far… 111 Next Up 112 9. Host an Architecture Design Studio . . . . . . 113 Plan an Architecture Design Studio 113 Choose Appropriate Design Activities 119 Invite the Right Participants 120 Manage the Group 122 Work with Remote Teams 124 Project Lionheart: The Story So Far… 126 Next Up 126 10. Visualize Design Decisions . . . . . . . . . 129 Show the Architecture from Different Views 129 Draw Fantastic Diagrams 136 Project Lionheart: The Story So Far… 141 Next Up 142 11. Describe the Architecture . . . . . . . . . 143 Tell the Whole Story 143 Match the Description Method to the Situation 145 Respect Your Audience 149 Organize Views around Stakeholders’ Concerns 152 Explain the Rationale for Your Decisions 155 Project Lionheart: The Story So Far… 156 Next Up 157 12. Give the Architecture a Report Card . . . . . . 159 Evaluate to Learn 159 Test the Design 160 Host an Evaluation Workshop 166 Evaluate Early, Evaluate Often, Evaluate Continuously 171 Project Lionheart: The Story So Far… 175 Next Up 176 13. Empower the Architects on Your Team . . . . . . 177 Promote Architectural Thinking 177 Facilitate Decision Making and Foster Skills Growth 179 Contents • viii Create Opportunities for Safe Practice 179 Delegate Design Authority 181 Design Architecture Together 185 Project Lionheart: The Epic Conclusion 186 Next Up 187 Part III — The Architect’s Toolbox 14. Activities to Understand the Problem . . . . . . 191 Activity 1. Choose One Thing 192 Activity 2. Empathy Map 195 Activity 3. Goal-Question-Metric (GQM) Workshop 199 Activity 4. Interview Stakeholders 202 Activity 5. List Assumptions 205 Activity 6. Quality Attribute Web 207 Activity 7. Mini-Quality Attribute Workshop 210 Activity 8. Point-of-View Mad Lib 215 Activity 9. Response Measure Straw Man 219 Activity 10. Stakeholder Map 221 15. Activities to Explore Potential Solutions . . . . . 225 Activity 11. Personify the Architecture 226 Activity 12. Architecture Flipbook 228 Activity 13. Component Responsibility Collaborator Cards 232 Activity 14. Concept Map 236 Activity 15. Divide and Conquer 239 Activity 16. Event Storming 244 Activity 17. Group Posters 249 Activity 18. Round-Robin Design 252 Activity 19. Whiteboard Jam 255 16. Activities to Make the Design Tangible . . . . . . 259 Activity 20. Architecture Decision Records 260 Activity 21. Architecture Haiku 263 Activity 22. Context Diagram 265 Activity 23. Greatest Hits Reading List 267 Activity 24. Inception Deck 269 Activity 25. Modular Decomposition Diagram 272 Activity 26. Paths Not Taken 274 Activity 27. Prototype to Learn or Decide 276