Lean Architecture

More and more Agile projects are seeking architectural roots as
they struggle with complexity and scale - and they're seeking
lightweight ways to do it

• Still seeking? In this book the authors help
  you to find your own path

• Taking cues from Lean development, they can help steer
  your project toward practices with longstanding track records

• Up-front architecture? Sure. You can deliver an
  architecture as code that compiles and that concretely guides
  development without bogging it down in a mass of documents and
  guesses about the implementation

• Documentation? Even a whiteboard diagram, or a CRC card,
  is documentation: the goal isn't to avoid documentation, but to
  document just the right things in just the right amount

• Process? This all works within the frameworks of Scrum,
  XP, and other Agile approaches

Autorentext

James O. Coplien is a writer, lecturer, and researcher in
the field of Computer Science. He has made key contributions in the
areas of software design and organizational development, software
debugging, and in empirical research. His early work on C++ idioms
was one of the three primary sources of the popular Design
Patterns. His work on Organizational patterns was an inspiration
for both Extreme Programming and for Scrum. Cope was a founding
Member of Hillside Group with Kent Beck, Grady Booch, Ward
Cunningham, Ralph Johnson, Ken Auer and Hal Hildebrand. He is
responsible for starting up several of the conferences in the
Pattern Languages of Programming (PLoP) conference series and is a
longstanding pattern author and PLoP shepherd.

Gertrud Bjornvig is an experienced software consultant
and trainer and has been in software development since 1984. She's
been working on development teams as a developer, analyst, and
project manager, and has had cross-organizational roles as
methodologist and process consultant. Her background is in
object-oriented development, including extensive work with UML and
RUP. Gertrud has been employed by Enator, Navision, Microsoft, and
TietoEnator, but since June 2007 she has been independent as a part
of Gertrud & Cope.

Gertrud holds a Master in Computer Science and Communication and is
one of the founders of Danish Agile User Group.

Zusammenfassung
More and more Agile projects are seeking architectural roots as they struggle with complexity and scale - and they're seeking lightweight ways to do it

• Still seeking? In this book the authors help you to find your own path
• Taking cues from Lean development, they can help steer your project toward practices with longstanding track records
• Up-front architecture? Sure. You can deliver an architecture as code that compiles and that concretely guides development without bogging it down in a mass of documents and guesses about the implementation
• Documentation? Even a whiteboard diagram, or a CRC card, is documentation: the goal isn't to avoid documentation, but to document just the right things in just the right amount
• Process? This all works within the frameworks of Scrum, XP, and other Agile approaches

Inhalt

About the Authors xii

Preface xiii

1 Introduction 1

1.1 The Touchstones: Lean and Agile 1

1.2 Lean Architecture and Agile Feature Development 4

1.3 Agile Production 7

1.3.1 Agile Builds on Lean 7

1.3.2 The Scope of Agile Systems 8

1.3.3 Agile and DCI 9

1.4 The Book in a Very Small Nutshell 10

1.5 Lean and Agile: Contrasting and Complementary 11

1.5.1 The Lean Secret 14

1.6 Lost Practices 14

1.6.1 Architecture 15

1.6.2 Handling Dependencies between Requirements 15

1.6.3 Foundations for Usability 16

1.6.4 Documentation 16

Code Does Not Stand Alone 17

Capturing the ''Why'' 19

1.6.5 Common Sense, Thinking, and Caring 19

1.7 What this Book is Not About 21

1.8 Agile, Lean Oh, Yeah, and Scrum and Methodologies and Such 22

1.9 History and Such 24

2 Agile Production in a Nutshell 27

2.1 Engage the Stakeholders 27

2.2 Define the Problem 29

2.3 Focusing on What the System Is: The Foundations of Form 30

2.4 Focusing on What the System Does: The System Lifeblood 32

2.5 Design and Code 33

2.6 Countdown: 3, 2, 1. . . 34

3 Stakeholder Engagement 35

3.1 The Value Stream 35

3.1.1 End Users and Other Stakeholders as Value Stream Anchors 36

3.1.2 Architecture in the Value Stream 37

3.1.3 The Lean Secret 38

3.2 The Key Stakeholders 41

3.2.1 End Users 43

Psyching Out the End Users 44

Don't Forget Behavior 46

The End User Landscape 47

3.2.2 The Business 47

A Special Note for Managers 48

3.2.3 Customers 50

. . . As Contrasted with End Users 50

''Customers'' in the Value Stream 52

3.2.4 Domain Experts 52

No Ivory Tower Architects 53

Experts in Both Problemand Solution Domains 54

3.2.5 Developers and Testers 55

3.3 Process Elements of Stakeholder Engagement 57

3.3.1 Getting Started 58

3.3.2 Customer Engagement 60

3.4 The Network of Stakeholders: Trimming Wasted Time 61

3.4.1 Stovepipe Versus Swarm 61

3.4.2 The First Thing You Build 64

3.4.3 Keep the Team Together 65

3.5 No Quick Fixes, but Some Hope 66

4 Problem Definition 67

4.1 What's Agile about Problem Definitions? 68

4.2 What's Lean about Problem Definitions? 68

4.3 Good and Bad Problem Definitions 70

4.4 Problems and Solutions 72

4.5 The Process Around Problem Definitions 73

4.5.1 Value the Hunt Over the Prize 73

4.5.2 Problem Ownership 74

4.5.3 Creeping Featurism 75

4.6 Problem Definitions, Goals, Charters, Visions, and Objectives 76

4.7 Documentation? 77

5 What the System Is, Part 1: Lean Architecture 79

5.1 Some Surprises about Architecture 80

5.1.1 What's Lean about This? 82

Deliberation and ''Pull'' 83

Failure-Proof Constraints or Poka-Yoke 83

The Lean Mantras of Conservation, Consistency, and Focus 84

5.1.2 What's Agile about Architecture? 84

It's All About Individuals and Interactions 84

Past Excesses 85

Dispelling a Couple of Agile Myths 86

5.2 The First Design Step: Partitioning 88

5.2.1 The First Partition: Domain Form Versus Behavioral Form 89

5.2.2 The Second Partitioning: Conway's Law 90

5.2.3 The Real Complexity of Partitioning 93

5.2.4 Dimensions of Complexity 94

5.2.5 Domains: A Particularly Interesting Partitioning 94

5.2.6 Back to Dimensions of Complexity 96

5.2.7 Architecture and Culture 100

5.2.8 Wrap-Up on Conway's Law 100

5.3 The Second Design Step: Selecting a Design Style 100 5.3.1 Contrasting Structuring w...