This document proposes rebooting Domain-Driven Design (DDD) by making it more accessible and continuing to develop the DDD toolbox. It suggests popularizing DDD by using less jargon and creating an open community of practitioners under the hashtag #DDDreboot. The goal is to make DDD more mainstream by working together to enrich the concepts and share knowledge.

1. #DDDREBOOT
LET’S REBOOT DDD!
THOMAS PIERRAIN - JEREMIE GRODZISKI
@TPIERRAIN - @JGRODZISKI

2. #DDDREBOOT
LET’S REBOOT DDD!
THOMAS PIERRAIN - JEREMIE GRODZISKI
@TPIERRAIN - @JGRODZISKI

3. #DDDREBOOT
BEFORE WE BEGIN

4. #DDDREBOOT#DDDREBOOT

5. #DDDREBOOT
DDD AROUND YOU?
OK, BUT 13 YEARS AFTER…
#DDDREBOOT

6. #DDDREBOOT
THERE MUST BE A
REASON…

7. #DDDREBOOT
« TACTICAL PATTERNS », « BOUNDED
CONTEXTS », « UBIQUITOUS LANGUAGE », ETC.
#DDDREBOOT
DOES IT NOT
MEAN ANYTHING
TO YOU?

8. #DDDREBOOT#DDDREBOOT

9. #DDDREBOOT
ACTUALLY
DDD…

10. #DDDREBOOT
DOMAIN DRIVEN
DESIGN, IS…

11. #DDDREBOOT
TO FOCUS ON
BUSINESS VALUE

12. #DDDREBOOT
OUR FIRST WORK AS DEVELOPER?
UNDERSTAND THE DOMAIN THAT
WE’LL HAVE TO CODE

13. #DDDREBOOT
A SET OF CONCEPTS THAT,
THROUGH USE CASES,
ALLOWS US TO SOLVE PROBLEMS
DOMAIN?

14. #DDDREBOOT
DOMAIN: DOUBLE ENTRY ACCOUNTING
SOLVED PROBLEMS: TRACKING, ROBUSTNESS
CONCEPTS: ACCOUNT, DEBIT, CREDIT, AMOUNT, ETC.

15. #DDDREBOOT
DOMAIN: IDE
SOLVED PROBLEMS: PRODUCTIVITY, INTEGRATION
CONCEPTS: PROJECTS, FILES, ANALYSIS, REFACTORING,
CVS, DEBUGGER, ETC.

16. #DDDREBOOT
BUT DDD IS
MOSTLY…

17. #DDDREBOOT #DDDREBOOT

18. #DDDREBOOT

19. #DDDREBOOT
AS DEVELOPERS, WE FACE …

20. #DDDREBOOT
3 LEVELS

21. #DDDREBOOT
IS / COMPANY
APPLICATION / TEAM
CODE / PAIR

22. #DDDREBOOT
IS / COMPANY
APPLICATION / TEAM
CODE / PAIR

23. #DDDREBOOT
IS / COMPANY
APPLICATION / TEAM
CODE / PAIR

24. #DDDREBOOT
LEVEL 1
IS / COMPANY
APPLICATION / TEAM
CODE / PAIR

25. #DDDREBOOT
QUESTION:
WHAT’S THE FOLLOWING CODE DOES?

26. #DDDREBOOT

27. #DDDREBOOT
SO?
#DDDREBOOT

28. #DDDREBOOT
DID YOU SEE SOME
CODE SMELLS?

29. #DDDREBOOT
Good code / Bad code

30. #DDDREBOOT
#1 MAGIC
NUMBERS

31. #DDDREBOOT
#1 MAGIC
NUMBERS
#2 DUPLICATIONS

32. #DDDREBOOT
#1 MAGIC
NUMBERS
#2 DUPLICATIONS
#3 PRIMITIVE
OBSESSION

33. #DDDREBOOT
#1 MAGIC
NUMBERS
#2 DUPLICATIONS
#3 PRIMITIVE
OBSESSION
#4 MIXED
CONCERNS
(TECH-BIZ)

34. #DDDREBOOT
#1 MAGIC
NUMBERS
#2 DUPLICATIONS
#3 PRIMITIVE
OBSESSION
#4 MIXED
CONCERNS
(TECH-BIZ)
#5 FUZZY
TERMINOLOGY
(

35. #DDDREBOOT
AND NOW CONCERNING THE
DOMAIN…

36. #DDDREBOOT
LET’S FIND
THE IMPLICITS !

37. #DDDREBOOT
FREE SHIPPING IF GREATER
THAN 100? 100 WHAT?

38. #DDDREBOOT
FIXED SHIPMENT COST?
FREE SHIPPING IF GREATER
THAN 100? 100 WHAT?

39. #DDDREBOOT
FIXED SHIPMENT COST?
FREE SHIPPING IF GREATER
THAN 100? 100 WHAT?
WEIGHT IN G? VARIABLE COST FOR
EACH SENT KG?

40. #DDDREBOOT
CURRENCY IN EUROS?
FIXED SHIPMENT COST?
WEIGHT IN G? VARIABLE COST FOR
EACH SENT KG?
FREE SHIPPING IF GREATER
THAN 100? 100 WHAT?

41. #DDDREBOOT
CURRENCY IN EUROS?
FIXED SHIPMENT COST?
WEIGHT IN G? VARIABLE COST FOR
EACH SENT KG?
SHIPPING OPTION?
FREE SHIPPING IF GREATER
THAN 100? 100 WHAT?

42. #DDDREBOOT
CURRENCY IN EUROS?
FIXED SHIPMENT COST?
WEIGHT IN G? VARIABLE COST FOR
EACH SENT KG?
SHIPPING OPTION?
FREE SHIPPING IF GREATER
THAN 100? 100 WHAT?
VARIABLE COST PER PRODUCT CATEGORY?

43. #DDDREBOOT
MAKE THE IMPLICIT,
EXPLICIT

44. #DDDREBOOT
DDD VERSION
#DDDREBOOT

45. #DDDREBOOT

46. #DDDREBOOT

47. #DDDREBOOT

48. #DDDREBOOT

49. #DDDREBOOT

50. #DDDREBOOT
VALUE TYPE

51. #DDDREBOOT
THE VALUE TYPE
EXPRESS YOUR DOMAIN AND
SWALLOW YOUR COMPLEXITY

52. #DDDREBOOT
-VALUE TYPES-
IT'S WHAT THEY ARE THAT IS IMPORTANT;
NOT WHO THEY ARE

53. #DDDREBOOT
-VALUE TYPES-
Σ OF ATTRIBUTES MEANING

54. #DDDREBOOT
-VALUE TYPES-
Example

55. #DDDREBOOT
-VALUE TYPES-
A COLOR (RGB: 255-255-0)
A SPEED OF 50 KM/H
A BANK NOTE OF 10 €
Examples

56. #DDDREBOOT
-VALUE TYPES-
IMMUTABLES BY DEFINITION
RICH WITH DOMAIN LOGIC
EQUALITY ON ATTRIBUTES
COMPOSABLES (OPERATORS, FONCTIONS)
AUTO-VALIDATING
Characteristics

57. #DDDREBOOT
-VALUE TYPES-
“TRANSACTIONAL” CONSTRUCTOR OR OPERATION
CONSTRAINTS ENFORCED BY THE CONSTRUCTOR, NOT BY THE OPERATIONS
FAIL FAST
NO SETTERS !
IMMUTABILITY, AUTO-VALIDATING
Implementation

58. #DDDREBOOT
-VALUE TYPES-
Implementation
RICH WITH DOMAIN LOGIC

59. #DDDREBOOT
-VALUE TYPES-
ON ALL THE ATTRIBUTES!
Implementation
STRONG UNICITY
hashCode
STRONG EQUALITY
equals

60. #DDDREBOOT
-VALUE TYPES-
“SIDE-EFFECT FREE” FUNCTIONS
out of the tar pit
WE COMPOSE, AND PREFER RÉ-ASSIGNING
INSTEAD OF CHANGING THE STATE LIKE BEFORE :-(

61. #DDDREBOOT
ESSENTIAL COMPLEXITY
ACCIDENTAL COMPLEXITY

62. #DDDREBOOT
« VALUE OBJECT »
#DDDREBOOT
IN DDD, WE NAME THAT:

63. #DDDREBOOT
« VALUE OBJECT »
#DDDREBOOT
IN DDD, WE NAME THAT:
OXYMORON

64. #DDDREBOOT
-VALUE TYPE-
ELECTED BEST R.O.I. OF DDD LAND

65. #DDDREBOOT
EXPRESS THE DOMAIN
CODEBASE PROGRESSIVE INTRODUCTION / EXEMPLARY
COMPLEXITY SWALLOWER
SIMPLIFY REASONING
(IMMUTABLE, THREAD-SAFE, TESTABLE)
- VALUE TYPE -
AN UNBEATABLE R.O.I.

66. #DDDREBOOT
PLANT THE SEED OF THE DOMAIN INTO THE CODE
THE VALUE TYPE

67. #DDDREBOOT
MAKE THE IMPLICIT,
EXPLICIT

68. #DDDREBOOT
SHIPPING COST DECISION TABLE

69. #DDDREBOOT
SHIPPING COST DECISION TABLE
DATA LITERALS!

70. #DDDREBOOT
AND, AS WE TALK ABOUT IMPLICIT…

71. #DDDREBOOT
"I CAN'T LISTEN TO
THAT MUCH WAGNER.
I START GETTING THE
URGE TO CONQUER
POLAND"
(WOODY ALLEN)

72. #DDDREBOOT
“I CAN’T SEE THAT MUCH
MANAGERS IN CODE.
I START GETTING TO…»
(JÉRÉMIE)

73. #DDDREBOOT
SHOOT THE
MANAGERS!
;-)

74. #DDDREBOOT
MAKE THE IMPLICIT,
EXPLICIT

75. #DDDREBOOT
ANOTHER PROBLEM

76. #DDDREBOOT#DDDREBOOT

77. #DDDREBOOT
LOST IN TRANSLATION #DDDREBOOT

78. #DDDREBOOT
"IT'S DEVELOPER'S UNDERSTANDING, NOT YOUR
KNOWLEDGE THAT BECOMES SOFTWARE!"
Alberto BRANDOLINI
(facing non collaborative BAs)

79. #DDDREBOOT
IN SOME
CASES…
#DDDREBOOT

80. #DDDREBOOT
SOLUTION?

81. #DDDREBOOT
SOLUTION?
1 LANGUAGE :
YOUR USERS’S ONE!

82. #DDDREBOOT
« THE UBIQUITOUS LANGUAGE »
#DDDREBOOT
IN DDD, IT’S NAMED:

83. #DDDREBOOT
YES BUT,
HOW DO WE DO WHEN…

84. #DDDREBOOT
A « CUSTOMER »
IT'S…

85. #DDDREBOOT
SO, HOW DO WE DO?

86. #DDDREBOOT
CONTEXT MATTERS

87. #DDDREBOOT
CONTEXT
A GROUP OF PERSONS SHARING THE SAME
MEANING BEHIND WORDS.

88. #DDDREBOOT
Context
CRM / Sales
Customer => Socio-
Economic group &
Center of Interest

89. #DDDREBOOT
Context
Accounting
Customer => Method of & Payment Period
Context
CRM / Sales
Customer => Socio-
Economic group &
Center of Interest

90. #DDDREBOOT
Context
Order-Shipment
Customer => addresses, availability
Context
Accounting
Customer => Method of & Payment Period
Context
CRM / Sales
Customer => Socio-
Economic group &
Center of Interest

91. #DDDREBOOT
« BOUNDED CONTEXT »
#DDDREBOOT
IN DDD, WE NAME THAT:

92. #DDDREBOOT
CRM / Sales
Context
Model and Language of Sales
Orders / Shipment
Context
Model & language of Logistics
Accounting Context
Model and Language of Accounting

93. #DDDREBOOT
CRM / Sales
Context
Model and Language of Sales
Orders / Shipment
Context
Model & language of Logistics
Accounting Context
Model and Language of Accounting
APP UI
WEB API
DATABASES APP UI
APP UI
APP UI DATABASES
WEB API
APP UI
APP UI
DATABASES
BATCH
USERS MANUAL
USERS MANUAL

94. #DDDREBOOT

95. #DDDREBOOT
CONTEXT
PRODUCTS
CATALOG
CONTEXT « SEARCH »
CONTEXT CLIENT & ORDERS
ADS CONTEXTCONTEXT “RECOMMANDATIONS"
CONTEXT « PROMOTIONS »
CONTEXT « PRODUCT HIGHLIGHTING »

96. #DDDREBOOT
LEVEL 2
IS / COMPANY
APPLICATION / TEAM
CODE / PAIR

97. #DDDREBOOT
PROBLEM

98. #DDDREBOOT#DDDREBOOT

99. #DDDREBOOT#DDDREBOOT
ONE THING
CHANGES AND…
#DDDREBOOT

100. #DDDREBOOT
WHY SO MUCH
DOMAIN TECHNICAL
STUFF IN OUR
CODEBASE?

101. #DDDREBOOT#DDDREBOOT

102. #DDDREBOOT
SOLUTION?
HEXAGONAL
ARCHITECTURE

103. #DDDREBOOT
THE WORLD DIVIDES IN 2
CATEGORIES…
#DDDREBOOT

104. #DDDREBOOT
OUTSIDE
INSIDE

105. #DDDREBOOT
DOMAIN
INFRA
(HTTP, Db, MoM,…)

106. #DDDREBOOT
DOMAIN
CODE
DO NOT ENTER
BUSINESS CODE
ONLY
INFRA CODE
(Ports & Adapters DMZ)

107. #DDDREBOOT
DOMAIN
CODE
DO NOT ENTER
BUSINESS CODE
ONLY
INFRA CODE
>> playground <<

108. #DDDREBOOT
OUTSIDE
INSIDE

109. #DDDREBOOT
HEXAGONAL ≠LAYERS

110. #DDDREBOOT
LAYERS ARCHITECTURE
+—————————+
| PRESENTATION |
+—————————+
| DOMAIN |
+—————————+
| DATABASE |
+—————————+

111. #DDDREBOOT
+———————————————+
| PRESENTATION | DATABASE | … |
+———————————————+
| DOMAIN |
+———————————————+
HEXAGONAL ARCHITECTURE

112. #DDDREBOOT
« Hexagonal
Architecture ?!?
(…)
That pattern is
fucking awesome! »

113. #DDDREBOOT
ANOTHER PROBLEM

114. #DDDREBOOT
LEGACY
NAM’
#DDDREBOOT

115. #DDDREBOOT
LEGACY
NAM’
#DDDREBOOT

116. #DDDREBOOT
LEGACY
NAM’
(WAGNER’S VERSION)

117. #DDDREBOOT
THE RECURRING QUESTION:
DO WE REBUILD
EVERYTHING FROM
SCRATCH OR NOT?

118. #DDDREBOOT
Legacy Application
Context

119. #DDDREBOOT
Legacy Application
Context
Well-crafted DDD
Bubble Context

120. #DDDREBOOT
Well-crafted DDD
Bubble Context
ANTI-CORRUPTION
LAYER
Legacy Application
Context

121. #DDDREBOOT
LEVEL 3
IS / COMPANY
APPLICATION / TEAM
CODE / PAIR

122. #DDDREBOOT
THE PROBLEM

123. #DDDREBOOT#DDDREBOOT

124. #DDDREBOOT#DDDREBOOT

125. #DDDREBOOT#DDDREBOOT

126. #DDDREBOOT
EVEN FOR
#DDDREBOOT
RELATIONS BASED ON
POWER

127. #DDDREBOOT
MAKE THE IMPLICIT,
EXPLICIT

128. #DDDREBOOT#DDDREBOOT
CONTEXT MAP EXPLICITS THE
RELATIONS OF “POWER”
BETWEEN TEAMS

129. #DDDREBOOT
UPSTREAM / DOWNSTREAM
« IF YOU ARE UPSTREAM
AND YOU POLLUTE THE
RIVER… … PEOPLE DOWNSTREAM
WILL BE IMPACTED. NOT
THE INVERSE. »
METAPHOR OF THE RIVER FLOW

130. #DDDREBOOT
« Search »
Context
Upstream
downstream
Products Catalog
Context
CONTEXT MAP

131. #DDDREBOOT
« Search »
Context
U
d
Products Catalog
Context
CONTEXT MAP
AN
TI-CO
RRU
PTIO
N
LAYER

132. #DDDREBOOT
UPSTREAM / DOWNSTREAM
CUSTOMER - SUPPLIER
CONFORMIST
ANTI-CORRUPTION LAYER (ACL)
SERVICE HOST
SHARED KERNEL
…
SOME VOCABULARIES AND PATTERNS

133. #DDDREBOOT
« CONTEXT MAP & STRATEGIC DESIGN »
#DDDREBOOT
IN DDD, WE NAME THAT:

134. #DDDREBOOT
SO…

135. #DDDREBOOT
BEFORE LEAVING

136. #DDDREBOOT
DOMAIN DRIVEN
DESIGN, IS…

137. #DDDREBOOT
A LOT MORE
ACCESSIBLE & USEFUL
THAN IT MIGHT SEEMS

138. #DDDREBOOT
STARTING MONDAY

139. #DDDREBOOT
Ubiquitous Language
Value types
Entities
Aggregates
Repositories
Factories
Services
Domain Events
Model Driven Design
Core Domain / Generic
Subdomains
Hexagonal Architecture*
CQRS*
Event Sourcing*
Bubble Context
Bounded Contexts
Context Maps
Anti-corruption Layer
Event storming
Customer / Supplier
Distillation
Shared Kernel
Conformist
…
CODE LEVEL
APP LEVEL
ENTREPRISE LEVEL
DDD
BUILDING
BLOCKS
* : not DDD but friendly

140. #DDDREBOOT
ON THE SHOULDERS OF GIANTS

141. #DDDREBOOT#DDDREBOOT
THANK YOU
ERIC !

142. #DDDREBOOT
BUT SOMETIMES…

143. #DDDREBOOT#DDDREBOOT
LET’S REBOOT DDD!

144. #DDDREBOOT#DDDREBOOT
LET’S REBOOT DDD!
AN OPEN COMMUNITY OF PRACTITIONERS

145. #DDDREBOOT#DDDREBOOT
LET’S REBOOT DDD!
AN OPEN COMMUNITY OF PRACTITIONERS
1. POPULARISING DDD BY BEING MORE ACCESSIBLE JARGON

146. #DDDREBOOT#DDDREBOOT
LET’S REBOOT DDD!
AN OPEN COMMUNITY OF PRACTITIONERS
1. POPULARISING DDD BY BEING MORE ACCESSIBLE JARGON
2. CONTINUE TO ENRICH THE DDD TOOLBOX

147. #DDDREBOOT#DDDREBOOT
LET’S REBOOT DDD!
1. POPULARISING DDD BY BEING MORE ACCESSIBLE JARGON
2. CONTINUE TO ENRICH THE DDD TOOLBOX
AN OPEN COMMUNITY OF PRACTITIONERS

148. #DDDREBOOT#DDDREBOOT
LET’S REBOOT DDD!
@DDDreboot +
ALL TOGETHER
LET’S MAKE DDD MAINSTREAM

149. #DDDREBOOT#DDDREBOOT
LET’S REBOOT DDD!
1. POPULARISING DDD BY BEING MORE ACCESSIBLE JARGON
2. CONTINUE TO ENRICH THE DDD TOOLBOX
@DDDreboot +
AN OPEN COMMUNITY OF PRACTITIONERS