DDD Basics: Bounded Contexts, Modelling - Kortrijk Edition

Two of the six modules of the @DDDBE meetup on Strategic Domain-Driven Design on June 10, 2014 at Stack & Heap

1. Bounded Contexts
2. Modelling

More at http://verraes.net/ or http://twitter.com/mathiasverraes

Transcript

1. DDD Basics - Kortrijk Edition
   June 10, 2014 - Belgium
   @DDDBE — http://domaindriven.be
   

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2. Kindly hosted by
   

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3. We’ve got some great
   (international) speakers,
   but we need locations!
   ping
   @DDDBE
   http://domaindriven.be
   

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4. Aspects of
   Domain-Driven Design
   

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5. Tactical DDD
   !
   design patterns
   

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6. Collaborative DDD
   !
   model storming
   

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7. Strategic DDD
   !
   complexity, scale
   

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8. Defining DDD (Yves)
   Ubiquitous Language (Jef)
   Bounded Contexts (Mathias)
   Context Mapping (Stijn)
   Modelling (Mathias)
   Starting/Selling DDD (Tom)
   Q&A / Lean Coffee
   

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9. Bounded Contexts
   

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10. “When something
    is wrong,
    something is
    too big.”
    — Leopold Kohr
    

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11. Large complex systems:
    harder to reason about
    

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12. Large complex systems:
    your mental model
    !=
    my mental model
    

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13. Large complex systems:
    subtle nuances
    in meaning
    

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14. Avoid a big unified
    centralised model.
    

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15. Classic example:
    What is a product?
    

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16. Split into
    Bounded Contexts
    

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17. Make Bounded Context
    explicit
    pure
    independent
    consistent within its
    boundary
    

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18. Benefits:
    clarity
    model integrity
    freedom to
    evolve separately
    

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19. Drawbacks:
    short term convenience
    choosing the boundaries
    how big is the problem?
    

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20. Tricks
    

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21. Inspired by
    departments
    teams
    life cycles
    business processes
    

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22. What if this was an
    off-the-shelf solution?
    

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23. How much
    communication goes on
    between Bounded
    Contexts?
    

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24. Visualize!
    !
    Context Mapping
    Model Storming
    

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25. Modelling
    

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26. Structural modelling
    describes state
    

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27. Structural modelling
    inspired by
    persistence concerns
    

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28. Relational
    Normalised
    CRUD
    Anaemic
    

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29. “CRUD is our
    industry’s
    grand failure.”
    — Greg Young
    

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30. Ask your Domain Expert
    about
    State Changes!
    

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31. Why does it change?
    When does it change?
    How often?
    Who causes it?
    By which rules?
    What consequences?
    

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32. !
    !
    The moving parts are
    more interesting than the
    stable parts
    

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33. !
    !
    A Domain Model
    is about:
    

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34. state + structure
    behaviour + change
    temporal
    roles + actors
    business rules + invariants
    causality + correlation
    interaction
    processes
    workflows + transitions
    intention + consequence
    failure …
    

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35. Modelling:
    Make the implicit explicit
    

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36. example
    !
    Intentions:
    Command Objects
    Consequences:
    Domain Events
    

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37. Intention
    Protection
    Interpretation
    Automation
    user sends Commands
    manage processes
    domain model
    
    sends Events,
    
    guards consistency
    create read models
    from Events
    DTO
    Commands
    Events
    

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38. @mathiasverraes
    http://verraes.net
    

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