Extreme DDD modelling
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What happens when you have the luxury of leading software projects without trade-offs and you're a Domain-Driven Design fanatic? You start stretching DDD concepts until it hurts and make experiments un uncharted territory. In this talk, we'll see a few unconventional approached to Context Mapping and what happens when you fully embrace CQRS and Small Aggregates as a modeling paradigm.
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Extreme DDD modelling
- 2. About me • Coding since 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
- 4. In the meanwhile Working in 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
- 7. Bounded Context • Unit of language consistency • A single model tailored around a specific purpose Bounded Context
- 8. Why do I care so much?
- 12. 2) A safe space for • Learning domain complexity • Experimenting • Delivering high value software Bounded Context
- 13. Motivation • Autonomy • Mastery • Purpose https://vimeo.com/15488784
- 14. Bounded Context • Unit of autonomy • Unit of mastery • Unit of purpose Bounded Context
- 15. Contexts on a Grid What to do when you have too many business lines?
- 16. Practice: Small company (5 people 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 Is Trainings a Bounded Context? Finance
- 20. “Phases” may help Warning: the order may change in different lines
- 22. Bounded Contexts on a grid 🙂 Shapes and Distribution Matters 🧐 Commonalities are visible 🧐 More precise names & purposes 😎 Better project structure in the IDE
- 23. On a single business line… It’s a value creation network!
- 24. Contexts on a Stack Too much domain expertise can be a problem
- 25. New Scenario Larger and more mature organization(s) Building sophisticated services on top of in-house technology Platform services available, but really complex
- 26. A small context map… Apparently Enough Bandwidth to support collaboration Still High Value Services are locked in Conformist mode !
- 27. It’s a Stack!
- 28. The solution is “By The Book”
- 29. … but it’s very hard to accept! We’re not an external model! We are your friends! You just need to get familiar with our API
- 30. 💡 Double API Layer Client-friendly API Server-side API
- 31. Why is it so hard?
- 32. Naming Trap Why are you developing your own APIs? We already provided Ours! Am I Paying twice for the same thing???
- 33. Expertise Trap
- 34. Very Hard to unlearn complexity once you master it
- 35. Solution is literally By the Book
- 36. Problem is in the human side
- 38. 💡 Fairytale programming “Coding against 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 he just said: ‘maximise ignorance’?"£
- 40. Yep!
- 41. The Customer Journey Problem Are we in Fairyland again?
- 42. Example: a payment system This is NOT the command we send !
- 43. Is it the same 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 language on the table
- 45. DDD Expert Fallacy I finally understand this domain complexity! Now everybody else should! Let’s Expose our Bounded Contexts to the world!
- 46. The world doesn’t care!
- 47. How does this language look like?
- 48. A flattened simplified language, throughout the whole experience Local languages with a deeper understanding of the complexity Some terms are obviously the same (but some may differ)
- 49. Customer Journey as a 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 our own blind spot
- 51. Question Time!
- 52. CQRS as if you mean it What you see is just an illusion
- 53. Still my company… Public Training Classes - Before the virus 🦠 🙂 Selling tickets online, obvious stuff… 😨 Class, Public and Event are relevant terms in our domain.
- 54. We eventStormed a little… Ticket Sold Registration Policy Register Attendee Public Training Edition Attendee Registered
- 56. Read Model Confirm Retire Amazing Workshop 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
- 58. Rules Scheduling a Training Class 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!
- 59. Except that
- 60. Other rules Some seats can 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 where people 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 Policies with “Always” and “Immediately” to make sure rules are not “rules” - (You have to speak and sound stupid to make it really work).
- 67. Magic!
- 68. Too many moving parts? Public Training Event Schedule Public Edition Scheduled Default Registration Policy Open Registration Training Class Registration Opened
- 69. We need some Glue 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 Whenever we 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 allow more flexibility
- 72. But I need to See the Training!!
- 74. Read Model Confirm Retire Amazing Workshop 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 a state Machine There!
- 77. That’s what you want to see!
- 78. There’s more than one!
- 79. I can show you Everything! I just need to see: UNCONFIRMED CONFIRMED RUNNING PAST CANCELED
- 80. User Perceived State Machine UNCONFIRMED CONFIRMED RUNNING PAST CANCELED
- 81. User Perceived State Machine 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 … … … …
- 82. Surprise states!
- 83. Extreme Read Model What a 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
- 84. Wrap up!
- 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 This is 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 Smaller Bricks 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 part of your model
- 90. Know Yours!
- 91. Question Time!
- 92. Thanks!
- 93. References • www.eventstorming.com • LeanPub books: • 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