Models, Modules, and Microservices

Talk last held on W-JAX 2019

Transcript

1. Starring With
   Directed by
   In the role of
   Also Starring
   

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5. H3NN1NG
   

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6. Schw3ntn3r
   

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7. @hschwentner
   

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9. Foto: Steindy/Wikipedia
   

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17. @hschwentner
    Do I get a car for this?
    

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20. CUSTOMER
    TELLS WISH FOR
    1
    SALESPERSON
    SIGNS
    TO
    GIVES
    FOR
    CONTRACT
    3
    RISIK MANAGER
    CONTRACT
    PASSES ON
    TO
    4
    CONTRACT
    VOTES
    CHECKS
    CALCULATES
    5
    6
    7
    CALCU-
    LATES
    TO
    8
    2
    CAR
    CREDIT
    RATING
    INSTALLMENT
    CAR
    RESALE
    VALUE
    CONTRACT
    

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21. @hschwentner
    How do we design a
    program for that?
    

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23. @hschwentner
    #dddesign
    

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24. @hschwentner
    Was ist das
    für 1 Design?
    

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25. @hschwentner
    Vong Domain her
    

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26. -DRIVEN DESIGN
    

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27. Software
    Domain
    

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31. CUSTOMER
    SIGNS
    CONTRACT
    3
    RISK MANAGER
    CONTRACT
    VOTES
    7
    <>
    LeasingContract
    sign()
    vote()
    

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32. <>
    LeasingContract
    sign()
    vote()
    

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33. Object orientation
    

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34. <>
    LeasingContract
    sign()
    vote()
    extend()
    terminate()
    sell_to_refinance()
    ...
    

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35. @hschwentner
    The One Big Model
    

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38. @hschwentner
    Reality:
    Not one big model
    But several mixed models
    

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39. BBOM
    Foto: Benutzer:Summi/Wikipedia/CC-BY-SA-3.0-migrated
    

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42. @hschwentner
    “Whoever uses a canonical model
    has lost control over his life.”
    – Karl Lagerfeld
    

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43. @hschwentner
    »Wer ein unternehmensweites
    Modell einsetzt, hat die Kontrolle
    über sein Leben verloren«
    – Karl Lagerfeld
    

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44. @hschwentner
    Why is that?
    

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47. @hschwentner
    Too Big
    to be understood
    as a whole
    

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50. @hschwentner
    Model?
    

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51. A tool to understand the
    world
    

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52. ?
    

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53. ?
    

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54. ?
    

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59. CUSTOMER
    TELLS WISH FOR
    1
    SALES-PERSON
    SIGNS
    TO
    GIVES
    FOR
    CONTRACT
    3
    RISIK MANAGER
    CONTRACT
    PASSES ON
    TO
    4
    CONTRACT
    VOTES
    CHECKS
    CALCULATES
    5
    6
    7
    CALCU-
    LATES
    TO
    8
    2
    CAR
    CREDIT
    RATING
    INSTALLMENT
    CAR
    RESALE
    VALUE
    CONTRACT
    SALES
    RISK MANAGMENT
    

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60. <>
    LeasingContract
    sign()
    vote()
    ✘
    

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61. <>
    LeasingContract
    sign()
    <>
    LeasingContract
    vote()
    

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62. <>
    LeasingContract
    sign()
    <>
    LeasingContract
    vote()
    SALES
    RISK
    MANAGEMENT
    

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63. Bounded Context
    

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64. <>
    LeasingContract
    sign()
    <>
    LeasingContract
    vote()
    SALES
    RISK
    MANAGEMENT
    

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66. @hschwentner
    Clear Boundaries
    

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68. @hschwentner
    Code
    Team
    Database
    

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69. @hschwentner
    Strategic Design
    

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70. ✘
    

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75. Team Head
    Team Tail
    Team Body
    Team Legs
    

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76. Team Emma
    Team Berta
    Team Erna
    Team Lisl
    

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77. <>
    LeasingContract
    sign()
    <>
    LeasingContract
    vote()
    

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78. @hschwentner
    Implementing
    Multiple Models
    

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79. @hschwentner
    JVM:
    Packages
    Jigsaw-Modules
    

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80. @hschwentner
    .NET:
    DLLs
    

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81. @hschwentner
    PHP:
    Namespaces
    

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82. @hschwentner
    JavaScript:
    Revealing Module Pattern
    TypeScript:
    Modules
    

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83. @hschwentner
    Generally:
    Microservices
    Self-Contained Systems
    Verticals
    

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84. @hschwentner
    Multiple Models in Java
    

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85. @hschwentner
    How?
    

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86. Packages
    

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87. @hschwentner
    1 bounded context
    =
    1 package
    

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88. package leasingninja.sales;
    class LeasingContract { /*...*/ }
    package leasingninja.riskmanagement;
    class LeasingContract { /*...*/ }
    

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89. <>
    LeasingContract
    sign()
    <>
    LeasingContract
    vote()
    <>
    leasingninja.sales
    <>
    leasingninja.riskmanagement
    

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90. Problems:
    * No real encapsulation
    * No nesting
    * only a logical group of
    classes
    

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91. Only public and package
    private
    

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92. But: all classes of a bounded
    context in one package ->
    already quite ok
    

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93. @hschwentner
    Project Jigsaw
    

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94. @hschwentner
    Real capsule
    

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95. @hschwentner
    package leasingninja.sales.ui;
    package leasingninja.sales.domain;
    package leasingninja.sales.infrastructure;
    

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96. @hschwentner
    package leasingninja.sales.ui;
    package leasingninja.sales.domain;
    package leasingninja.sales.infrastructure;
    package leasingninja.sales.api;
    

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97. @hschwentner
    /*
    module-info.java
    */
    module leasingninja.sales {
    exports leasingninja.sales.api;
    }
    

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98. leasingninja.sales.api
    leasingninja.sales.*
    Interface
    Not accessible
    from outside
    

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99. @hschwentner
    /*
    module-info.java
    */
    module leasingninja.riskmanagement {
    requires leasingninja.sales;
    }
    

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100. RISK
     MANAGE-MENT
     SALES
     

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101. Rule:
     reverse domain names
     

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102. @hschwentner
     /*
     module-info.java
     */
     module de.wps.leasingninja.sales {
     exports de.wps.leasingninja.sales.api;
     }
     

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103. @hschwentner
     /*
     module-info.java
     */
     module de.wps.leasingninja.riskmanagement {
     requires de.wps.leasingninja.sales;
     }
     

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104. @hschwentner
     Modular JAR
     

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105. @hschwentner
     Maybe even better fitting:
     services mit
     uses/provides with
     

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106. @hschwentner
     Multiple Models in .NET
     

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107. @hschwentner
     How?
     

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108. Assembly
     

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109. @hschwentner
     1 bounded context
     =
     1 DLL
     

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110. namespace Leasingninja.Sales
     {
     class LeasingContract { /*...*/ }
     }
     namespace Leasingninja.Riskmanagement;
     {
     class LeasingContract { /*...*/ }
     }
     

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111. <>
     LeasingContract
     sign()
     <>
     LeasingContract
     vote()
     <>
     Leasingninja.Sales
     <>
     Leasingninja.Riskmanagement
     

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112. @hschwentner
     Architecture inside a
     Bounded Context (DLL)
     

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113. @hschwentner
     namespace Leasingninja.Sales.UI {}
     namespace Leasingninja.Sales.Application {}
     namespace Leasingninja.Sales.Domain {}
     namespace Leasingninja.Sales.Infrastructure {}
     

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114. @hschwentner
     namespace Leasingninja.Sales.UI {}
     namespace Leasingninja.Sales.Application {}
     namespace Leasingninja.Sales.Domain {}
     namespace Leasingninja.Sales.Infrastructure {}
     namespace Leasingninja.Sales {}
     

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115. @hschwentner
     namespace Leasingninja.Sales.Domain
     {
     [Entity]
     internal class LeasingContract { /*...*/ }
     }
     namespace Leasingninja.Sales
     {
     [DomainEvent]
     public class ContractSigned { /*...*/ }
     }
     

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116. Leasingninja.Sales
     Leasingninja.Sales.UI
     Leasingninja.Sales.Application
     Leasingninja.Sales.Domain
     Leasingninja.Sales.Infrastructure
     Interface
     Not accessible
     from outside
     

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117. RISK
     MANAGE-MENT
     SALES
     

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118. @hschwentner
     Multiple Models in PHP
     

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119. @hschwentner
     How?
     

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120. Namespace
     

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121. @hschwentner
     1 bounded context
     =
     1 namespace
     

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122. namespace Leasingninja\Sales;
     class LeasingContract { /*...*/ }
     >
     namespace Leasingninja\Riskmanagement;
     class LeasingContract { /*...*/ }
     >
     

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123. FQCN
     (Fully qualified class name =
     full namespace + class name)
     

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124. <>
     LeasingContract
     sign()
     <>
     LeasingContract
     vote()
     <>
     Leasingninja.Sales
     <>
     Leasingninja.Riskmanagement
     

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125. Problems:
     * No encapsulation
     * only a logical group of
     classes
     

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126. But: all classes of a bounded
     context in one namespace ->
     better than nothing
     

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127. @hschwentner
     Architecture inside a
     Bounded Context
     

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128. @hschwentner
     namespace Leasingninja\Sales\UI;
     namespace Leasingninja\Sales\Application;
     namespace Leasingninja\Sales\Domain;
     namespace Leasingninja\Sales\Infrastructure;
     

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129. @hschwentner
     namespace Leasingninja\Sales\UI;
     namespace Leasingninja\Sales\Application;
     namespace Leasingninja\Sales\Domain;
     namespace Leasingninja\Sales\Infrastructure;
     namespace Leasingninja\Sales;
     

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130. Leasingninja.Sales
     Leasingninja.Sales.UI
     Leasingninja.Sales.Application
     Leasingninja.Sales.Domain
     Leasingninja.Sales.Infrastructure
     Interface
     (should)
     not be
     accessible from
     outside
     

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131. Convention:
     Access only 1 dot
     2 dot only in same BC
     

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132. RISK
     MANAGE-MENT
     SALES
     

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134. @hschwentner
     Multiple Models with
     Microservices
     

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138. Distributed System
     

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139. Fallacies of distributed
     computing:
     The network is reliable.
     Latency is zero.
     Bandwidth is infinite.
     The network is secure.
     Topology doesn't change.
     There is one administrator.
     Transport cost is zero.
     The network is homogeneous.
     

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140. Verticals
     Self-Contained Systems
     Microservices
     

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143. Micro-
     service A
     Presentation
     Domain
     Infrastructure
     Application
     Micro-
     service B
     Direct Access
     to DB
     Micro-
     service C
     

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144. ✘
     

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148. @hschwentner
     Independent Deployability
     

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149. Team Emma
     Team Berta
     Team Erna
     Team Lisl
     

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150. Team Emma
     Team Berta
     Team Erna
     Team Lisl
     

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151. Team Emma
     Team Berta
     Team Erna
     Team Lisl
     
     

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152. RISK
     MANAGE-MENT
     SALES
     

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153. RISK
     MANAGE-MENT
     

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154. RISK
     MANAGE-MENT
     SALES
     

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155. @hschwentner
     Core Domain
     

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156. Team Emma
     Team Berta
     Team Erna
     Team Lisl
     

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157. Team Emma
     Team Berta
     Team Erna
     Team Lisl
     

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160. RISK
     MANAGE-MENT
     SALES
     

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162. @hschwentner
     How to split the monolith
     

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163. 1) How should it be?
     2) How is it?
     3) How to move the “is” to the “ideal”?
     RISK
     MANAGE-
     MENT
     SALES
     

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164. 1) How should it be?
     1) Collaborative Modelling
     2) “ideal” context map
     2) How is it?
     1) Architecture Analysis
     2) As-is context map
     3) How to move the “is” to the “ideal”?
     1) Extract a supporting domain to learn
     2) Then extract core(s)
     

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165. <>
     LeasingContract
     sign()
     vote()
     SALES
     RISK
     MANAGEMENT
     <>
     LeasingContract
     sign()
     vote()
     BIG BALL
     OF MUD
     <>
     LeasingContract
     sign()
     vote()
     

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166. @hschwentner
     Always Microservices?
     

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167. Simon Brown
     

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168. Distributed
     Big Ball Of Mud
     Modulith Microservices
     Monolithic
     Big Ball Of Mud
     

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170. @hschwentner
     Consulting
     

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171. @hschwentner
     Team organization
     

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175. “Organizations which design systems
     are constrained to produce designs
     which are copies of the
     communication structures of
     these organizations.”
     Melvin Conway
     

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176. Melvin Conway
     (1967)
     “Organizations which design systems
     are constrained to produce designs
     which are copies of the
     communication structures of
     these organizations.”
     

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177. “The organization of the software and
     the organization of the software team
     will be congruent.”
     Eric Raymond
     

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178. “If you have four groups working on a compiler,
     you'll get a 4-pass compiler.”
     Eric Raymond
     

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179. @hschwentner
     Conclusion
     

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180. 1. Model your domain
     2. Split => several models
     (3. Distribute models)
     

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181. Strategic Design must
     Microservices can
     

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182. @hschwentner
     Further Reading
     

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183. @hschwentner
     LeasingNinja.io
     

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184. @hschwentner
     speakerdeck.com/hschwentner
     

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185. Foto: H. Schwentner
     

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186. Foto: H. Schwentner
     

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187. Foto: Amazon
     

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190. 15$ online:
     leanpub.com/domainstorytelling
     Frag mich nach
     Deiner Kopie
     Einführung mit allem
     was man wissen muss
     Überblick
     Rabatt!
     https://leanpub.com/domainstorytelling/c/wjax2019
     

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191. @hschwentner
     What now?
     

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192. @hschwentner
     Consulting
     

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194. Workshop
     Domain-Driven Design concrete
     wps.de/ddd
     

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195. @hschwentner
     Foto: Henning Schwentner
     

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199. @hschwentner
     FEEDBACK
     

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206. Henning Schwentner
     @hschwentner
     hs@wps.de
     DDD
     DDD
     Slides: speakerdeck.com/hschwentner
     Book: leanpub.com/domainstorytelling
     

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