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Extreme DDD modelling
The document discusses extreme domain-driven design (DDD) modeling and context mapping, focusing on bounded contexts as units of language, autonomy, and purpose within software development. It emphasizes the importance of clear boundaries, understanding domain complexity, and ensuring user-centered design, particularly in client API development and customer journeys. Additionally, it highlights the complexities of managing business lines and the need for flexible policies while addressing common challenges such as expertise and naming traps.
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Extreme DDD modelling
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- 2. About me • Codingsince 1982 • Into Domain-Driven Design since 2005 • running www.avanscoperta.it • Modelling (almost) everything with sticky notes, markers and a paper roll. • Calling this stuff
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- 4. In the meanwhile Workingin stealth mode on internal projects Hey, …I am the Boss! Assisting a few selected customers
- 5. About This Talk •Unconventional Context Mapping • Small Q&A • CQRS as you mean it • Q&A • Virtual Hugs & Good byes
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- 7. Bounded Context • Unitof language consistency • A single model tailored around a specific purpose Bounded Context
- 8. Why do Icare so much?
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- 12. 2) A safespace for • Learning domain complexity • Experimenting • Delivering high value software Bounded Context
- 13. Motivation • Autonomy • Mastery •Purpose https://vimeo.com/15488784
- 14. Bounded Context • Unitof autonomy • Unit of mastery • Unit of purpose Bounded Context
- 15. Contexts on aGrid What to do when you have too many business lines?
- 16. Practice: Small company (5people core - about 20 partners) Many Business Lines 🤔 No departments or Roles to look at 😊 EventStorming as a common practice 🙄 But only on a few Business Lines 😏 …writing specific & General Purpose code.
- 17. Possible Bounded Contexts Trainings Consulting Planning Marketing Sales Billing Logistics Webinars IsTrainings a Bounded Context? Finance
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- 20. “Phases” may help Warning:the order may change in different lines
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- 22. Bounded Contexts ona grid 🙂 Shapes and Distribution Matters 🧐 Commonalities are visible 🧐 More precise names & purposes 😎 Better project structure in the IDE
- 23. On a singlebusiness line… It’s a value creation network!
- 24. Contexts on aStack Too much domain expertise can be a problem
- 25. New Scenario Larger andmore mature organization(s) Building sophisticated services on top of in-house technology Platform services available, but really complex
- 26. A small contextmap… Apparently Enough Bandwidth to support collaboration Still High Value Services are locked in Conformist mode !
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- 28. The solution is“By The Book”
- 29. … but it’svery hard to accept! We’re not an external model! We are your friends! You just need to get familiar with our API
- 30. 💡 Double APILayer Client-friendly API Server-side API
- 31. Why is itso hard?
- 32. Naming Trap Why areyou developing your own APIs? We already provided Ours! Am I Paying twice for the same thing???
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- 34. Very Hard tounlearn complexity once you master it
- 35. Solution is literally Bythe Book
- 36. Problem is inthe human side
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- 38. 💡 Fairytale programming “Codingagainst the system I wish I had” Design your APIs according to your current needs In an ACL implement mapping according to what you’re given. Goal: “Maximise Ignorance about the underlying complexity”
- 39. “… did hejust said: ‘maximise ignorance’?"£
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- 41. The Customer Journey Problem Arewe in Fairyland again?
- 42. Example: a paymentsystem This is NOT the command we send !
- 43. Is it thesame thing? • GUI elements need to be aligned with the user mental model • “Call To Action” is designed to be catchy • Underlying commands need to be precise, and tend to follow local symmetries (like CalculateFee / FeeCalculated) Send Money
- 44. One more languageon the table
- 45. DDD Expert Fallacy Ifinally understand this domain complexity! Now everybody else should! Let’s Expose our Bounded Contexts to the world!
- 46. The world doesn’tcare!
- 47. How does this languagelook like?
- 48. A flattened simplified language, throughoutthe whole experience Local languages with a deeper understanding of the complexity Some terms are obviously the same (but some may differ)
- 49. Customer Journey asa BC Customer Language DESIGNED (engagement, simplicity, mental model, AB testing) FLAT (we don’t want to teach DDD to our users) Proxy stakeholders (for many reasons) Server Language(s) Real Stakeholders & Departments Emerging and Evolving (driven by purpose)
- 50. We built ourown blind spot
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- 52. CQRS as ifyou mean it What you see is just an illusion
- 53. Still my company… PublicTraining Classes - Before the virus 🦠 🙂 Selling tickets online, obvious stuff… 😨 Class, Public and Event are relevant terms in our domain.
- 54. We eventStormed alittle… Ticket Sold Registration Policy Register Attendee Public Training Edition Attendee Registered
- 56. Read Model Confirm Retire AmazingWorkshop With John Doe June 25 - 2020 90 days till deadline 5 of 16 ticket sold UNCONFIRMED Threshold at 8 - John Smith - Early Bird Ticket - Mario Rossi - Early Bird Ticket - Francesca Bianchi - Early Bird Ticket - Sylvie Bouchard - Standard Ticket - Nick Fury - Special Ticket The information needed to make a decision A few things are missing, I am lazy
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- 58. Rules Scheduling a TrainingClass allows registration Can’t sell more Tickets than the given capacity Can’t register participants after the sales closed Reaching threshold allows to confirm the training class Class confirmation triggers a message to the attendees Public Training Edition Piece of cake!
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- 60. Other rules Some seatscan be reserved before the class goes public Sales can happen on the phone too. Some last minute changes are still possible. We’d like to check messages before they’re sent. Ouch!
- 61. This is wherepeople lie Current rules are not carved in stone: they’re then best trade off between the state of the organisation and the market. They’re both going to change. Maybe they already did. Policy
- 62. #protip Validate your Policieswith “Always” and “Immediately” to make sure rules are not “rules” - (You have to speak and sound stupid to make it really work).
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- 68. Too many movingparts? Public Training Event Schedule Public Edition Scheduled Default Registration Policy Open Registration Training Class Registration Opened
- 69. We need someGlue Whenever a public training class is scheduled, we open registration. Default Registration Policy Private Sales Scheduling Policy Sales can be opened before a training class goes public.
- 70. Some more options Wheneverwe reach the Threshold we notify the registered attendees of the confirmation Training Confirmation Policy Whenever we cancel a training class we prepare a cancellation E-mail with personalised options. Orga nizer Training Cancellation Policy Orga nizer
- 71. Smaller Moving parts allowmore flexibility
- 72. But I needto See the Training!!
- 74. Read Model Confirm Retire AmazingWorkshop With John Doe June 25 - 2020 90 days till deadline 5 of 16 ticket sold UNCONFIRMED Threshold at 8 - John Smith - Early Bird Ticket - Mario Rossi - Early Bird Ticket - Francesca Bianchi - Early Bird Ticket - Sylvie Bouchard - Standard Ticket - Nick Fury - Special Ticket The information needed to make a decision Planning Registration Sales Product Design
- 75. Wait a Minute!I still need the aggregate!
- 76. I saw astate Machine There!
- 77. That’s what youwant to see!
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- 79. I can showyou Everything! I just need to see: UNCONFIRMED CONFIRMED RUNNING PAST CANCELED
- 80. User Perceived StateMachine UNCONFIRMED CONFIRMED RUNNING PAST CANCELED
- 81. User Perceived StateMachine Read Model Sales Event Time Stealth Closed Unconfirmed Future Confirmed Closed Confirmed Future Canceled Closed Canceled Future Unconfirmed Open Unconfirmed Future Confirmed Open Confirmed Future Error Open Canceled Future Forgot something? Closed Unconfirmed Present Running Closed Confirmed Present 😭😭😭😭😭😭😭 Closed Canceled Present Hey Wait a Minute! Open … Present … … … …
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- 83. Extreme Read Model Whata user need to see in order to take given decisions …according to the mental model of the user Tailored on user needs Tailored on user perception Confirm
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- 85. Extreme Context Mapping 💡Bounded Contexts on a Business Grid 💡 Bounded Contexts on a stack 💡 Customer Journey as a Separate Bounded Context Bounded Context
- 86. Policies as Glue Thisis where you want to implement flexibility This is where users often want still to have control I am more interested in shaping the conversation than constraining implementation. Policy
- 87. Aggregates as Bricks SmallerBricks allow for for more combinations … but also more code. Policy
- 88. Human Biases Matter Experts-> Join The BBom! Developers -> Automate Everything! Users -> I just need to see … A CRUD!
- 89. Biases are partof your model
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- 93. References • www.eventstorming.com • LeanPubbooks: • http://leanpub.com/introducing_eventstorming (still growing) • https://leanpub.com/ddd_first_15_years • Blog: • https://medium.com/@ziobrando • http://ziobrando.blogspot.com • Twitter: @ziobrando • Trainings & Workshop facilitation: info@avanscoperta.it • http://www.avanscoperta.it