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![Business-Driven Stressors
Can I have [This] without [That]?
Can I have [Reservations] without a [Ticket]?
Is this the Exception or the Rule?
It’s always a [Bundle], sometimes a simple one.
Can I have [This] and [That]?](https://image.slidesharecdn.com/extremedddmodelling2024devoxxpoland-240624153452-95c86c0b/75/Extreme-DDD-Modelling-Patterns-2024-Devoxx-Poland-61-2048.jpg)
Uploaded byAlberto Brandolini
Extreme DDD Modelling Patterns - 2024 Devoxx Poland
The document discusses the intricacies of domain-driven design, particularly focusing on challenges faced in small organizations regarding bounded contexts and model coherence. It emphasizes the importance of using a consistent language reflective of the specific domain while avoiding legacy pitfalls, highlighting the need for clarity in communication and modeling to prevent a 'big ball of mud' effect. Additionally, it explores practical approaches to event-driven architecture and the necessity of thoughtful integration of business elements in the design process.
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Extreme DDD Modelling Patterns - 2024 Devoxx Poland
- 1.
- 2. Disclaimer In Domain-Driven Designsince the early days In love with CQRS/ES and EventStorming Enjoying modelling without trade-offs Running My own company Unusual freedom Eating my own gourmet dogfood
- 3. The account thatwasn’t Quick intro
- 4. Context Simple Treasury Module:we need to know the available liquidity in different accounts Multiple account types, no integrations via API (we’re too small/lazy/Poor)
- 5. So… • We needan account. name currentBalance Account deposit withdraw
- 7. Pick your poison name currentBalance Account deposit withdraw Incoherent design Someone else’smodel bank Not the domain name name currentBalance lastUpdatedOn Account registerSnapshot trackOperation name currentBalance lastUpdatedOn AccountTracker registerSnapshot trackOperation
- 8. Consistent with User’s Expectation Coherentwith semantics name currentBalance lastUpdatedOn Account registerSnapshot trackOperation name currentBalance lastUpdatedOn AccountTracker registerSnapshot trackOperation 😵 Ubiquitous Language? Account
- 9. Labels can make youhappy Account
- 10. Danger Zone! • Whydid we pick the wrong model first? • Kahneman’s System one? • …There’s a little backdoor in our brain that allows school examples to bypass validation • Including examples from speakers on a stage name currentBalance Account deposit withdraw
- 11.
- 12. context Long Lasting Project(3+ Years) in a large organisation Complex domain with a very specific jargon Legacy core Glossary built with the best intentions Still trapped in special cases
- 13. The revelation Photo byJoshua Earle on Unsplash
- 14. Every single termfrom Marketing was crap!
- 15. I’ll follow you everywheremy beloved domain expert!! I have no clue where I am going…
- 16. Not every informationfrom the “expert” is suitable to become part of our model
- 17. Room Reservations Some areassigned at purchase time Some are assigned at departure time Rooms can be sold with ancillary services Upgrades are possible Money can buy almost everything
- 18. Labels can make youhappy All Inclusive Bundle Catalog Item Not cool enough to be mentioned by marketing
- 19. Maybe we’re notselling our inventory after all… Maybe we’re always selling a bundle, which sometimes is simple 🤔 🤔
- 20. A Flat Dictionarycan be a force in the wrong direction 💡 Make sure your Dictionary reflects your bounded contexts
- 21. Experts grown onlegacy, will guide you to rebuild the legacy
- 22. Complex Software inthe small Or: “how not to grow a Big Ball of Mud”
- 23. Bounded Context • Limitof applicability of a model • Unit of language consistency • A single model tailored around a specific purpose Bounded Context
- 24. Good, but notactionable
- 25. Proxies to therescue • Every proxy has a variable accuracy • Unfortunately, most of these proxies are only visible in large organisations Bounded Context Limit of applicability of a model Team Subdomain Organization Technology Legacy
- 26.
- 27. In small Organizations… •People, teams and department stop being relevant • Everything is pulling towards a monolith • All we’re left with is Purpose and Business Lines
- 28. Is this ourDestiny?
- 29. In the smallscale • Single database -> Flat Namespace • Single Project -> IDE doesn’t like Polysemic words • Small Team -> The Mental Model naturally tends towards a Flat Namespace
- 31. Designing to growright
- 32. Possible Bounded Contexts Trainings Consulting Planning Marketing Sales Billing Logistics Webinars IsTrainings a Bounded Context? Finance
- 34. Our idea: Separate onpurpose Logical separation only (easily reversible mistakes) See what happens
- 35. Mixing is cheaperthan Splitting
- 36.
- 37. Business Lines first! Books PublicTrainings Private Trainings Consulting Sponsorships Public Speaking Software Delivery Meetups Events Obvious in the large, but our responsibility in the small.
- 38. Then “Phases” Books Public Trainings PrivateTrainings Consulting Sponsorships Public Speaking Software Delivery Meetups Events Planning Sales Delivery Billing Product Design Financial Analysis Strategy Marketing Inventory
- 40. Where are theycoming from? 10 years of Orange Stickies on paper rolls? Independent forces for change? Some “standard” departments Gut Feeling? Perfection is not the goal
- 41. Then Purposes ->Models Something is still missing, but …you got the point Books Public Trainings Private Trainings Consulting Sponsorships Public Speaking Software Delivery Meetups Events Planning Sales Delivery Billing Product Design Financial Analysis Strategy Marketing Inventory Date Picking Tracking Value Tickets and discounts Print on Demand Personal Availability Engagement Strategy Deals Pricing Budget Contracts & Engagement Partnerships Forecast Global Analysis Billing Billing Scouting Date Picking Content design Review Logistics Scouting Courseware and certificates Newsletter & social Newsletter & social Content Design Format Design
- 42. Bounded Contexts ona grid 🙂 Shapes and Distribution Matters 🧐 Commonalities are visible 🧐 More precise names & purposes 😎 Better project structure in the IDE We definitely need a map! Books Public Trainings Private Trainings Consulting Sponsorships Public Speaking Software Delivery Meetups Events Planning Sales Delivery Billing Product Design Financial Analysis Strategy Marketing Inventory Date Picking Tracking Value Tickets and discounts Print on Demand Personal Availability Engagement Strategy Deals Pricing Budget Contracts & Engagement Partnerships Forecast Global Analysis Billing Billing Scouting Date Picking Content design Review Logistics Scouting Courseware and certificates Newsletter & social Newsletter & social Content Design Format Design
- 43. On a singlebusiness line… It’s a value-creation network! Looks a lot like EventStorming 😎 Public Trainings Planning Sales Delivery Billing Product Design Financial Analysis Strategy Marketing Inventory Tickets and discounts Deals Pricing Global Analysis Billing Date Picking Logistics Scouting Courseware and certificates Newsletter & social Content Design Reservations
- 44.
- 45. Modelling our ownflow(s) And being radical about it
- 46. The Draft-Executable-Tracking Archetype Draft ModelExecutable Tracking Easy to change, possibly partially specified Solid, running on read- only data Collecting or visualizing Validation Different Models, very similar languages, different paradigms
- 47. Visual Grammar Aggregate Read Model Command Value Object? Policy Event Person Unit of transactional consistency Somethingthat happened: verb in part tense Command Reactive logic: “Whenever (event) then (command) The information needed to decide Read Model External System
- 48. A little morecomplex: Design Planning Sales Inventory Logistics Tracking Training Summary Public Event Open Event Printables Venue Booking Ticket Sale Purchase Aggregate Read Model
- 49. A little morecomplex Design Planning Sales Inventory Logistics Tracking Training Summary Public Event Ticket Sale Open Event Printables Register Attendee Purchase Ticket Open Sales Schedule Confirm Cancel Close Sales Cancel Attendee Session Plan Ticket Plan …other possible Value Objects Open Registra tions (capacity) Close Registrations Venue Booking Purchase
- 50. Policies to connect-1 Design Planning Sales Inventory Logistics Tracking Training Summary Public Event Ticket Sale Open Event Printables Register Attendee Purchase Ticket Open Sales Schedule Confirm Cancel Close Sales Cancel Attendee Session Plan Ticket Plan … PublicTraining Event Coordination Open Registra tions (capacity) Close Registrations Venue Booking Purchase
- 51. Policies to connect-2 Design Planning Sales Inventory Logistics Tracking Training Summary Public Event Ticket Sale Open Event Printables Register Attendee Reserve Ticket Open Sales Schedule Confirm Cancel Close Sales Cancel Attendee Session Plan Ticket Plan … PTE Policy Open Registra tions (capacity) Close Registrations Registration Policy Ticket PurchasedAttendee Registered Courseware Policy One more! Venue Booking Purchase Ticket Reservation Policy Purchase Started Purchase Completed Assign Ticket
- 52. Read Models tosummarise Design Planning Sales Inventory Logistics Tracking Training Summary Public Event Ticket Sale Open Event Printables Register Attendee Purchase Ticket Open Sales Schedule Confirm Cancel Close Sales Cancel Attendee Session Plan Ticket Plan … PTE Policy Open Registra tions (capacity) Close Registrations Ticket Purchased Attendee Registered Event Confirmed Purchase
- 53.
- 54. Naming pain Design Planning Sales Inventory Logistics Tracking Training Summary Public Event Ticket Sale Open Event Printables Register Attendee Purchase Ticket Open Sales Schedule Confirm Cancel Close Sales Cancel Attendee Session Plan Ticket Plan … Public Training Event Coordination Policy Open Registra tions (capacity) Close Registrations Ticket Purchased Attendee Registered Event Confirmed Horriblenames Venue Booking Purchase Experts will Keep using the specific terms like “Meetup” “Training” or “Conference”
- 55.
- 56.
- 58. A single usecase might not be enough We are in the core: some principles are not dogmas 🤔 🤔
- 59.
- 60. Online Training Design Planning Sales Inventory Logistics Tracking Training Summary Public Event Ticket Sale Open Event Printables Register Attendee Purchase Ticket Open Sales Schedule Confirm Cancel Close Sales Cancel Attendee Session Plan Ticket Plan … Public Online Training Policy Open Registra tions (capacity) Close Registrations Registration Policy Ticket PurchasedAttendee Registered Courseware Policy One more! Delivery Online Session Schedule Start Purchase Very Limited changes, without opening boxes.
- 61. Business-Driven Stressors Can Ihave [This] without [That]? Can I have [Reservations] without a [Ticket]? Is this the Exception or the Rule? It’s always a [Bundle], sometimes a simple one. Can I have [This] and [That]?
- 62.
- 63. More Options Hybrid Trainings ComboTickets Composite Events Resellers and Partners Conferences and Workshops Books as Courseware
- 64. Top-Down Forces Interacting withDomain Experts Detecting Business Lines Imposing phases and archetypes
- 65. Bottom-Up Forces Detecting BuildingBlocks - Types Making Them Safe
- 66. Session Layout • Originallyok with int duration • Pandemic as a majestic stressor: • Exact Timing became vital information for online sessions • Empty spaces become interesting for different activity types Session Layout
- 68. Parallel Models Design Delivery Session Plan Session Type Session Session Duration Session Schedule Scheduled Session OnMay 17th On may 17th, 9:30 am 3 Days Day 1, 9:30 am Session Type Zoom Google Calendar
- 69.
- 70.
- 71. How much ofthis journey can involve domain experts? I suspect “It Depends” is a clear winner here. 🤔 🤔
- 72. Feeling guilty Design Delivery Session Plan Session Type Session Session Duration Session Schedule Scheduled Session Horriblenames On May 17th On may 17th, 9:30 am 3 Days Day 1, 9:30 am Session Type
- 73. Problem with thispattern? Experts think they’re talking about the same thing: You know they’re not Draft Model Executable Tracking Validation Propose Adjust Annotate Comment Finalize Schedule Cancel Session Session Type Session Session Type Duration Schedule Duration Comment Measure Start Join Terminate Session Session Type Duration
- 74. What is visible? Session Plan Ticket Plan Training Summary Schedule Public Event Ticket SaleOpen Event Session Type Session Session Duration Session Can Domain Experts help here?
- 75. State as anIllusion The final trick!
- 76. I’ll follow you everywheremy beloved domain expert!!
- 77. Read Model Con fi rm Retire AmazingWorkshop With John Doe June 25 - 2023 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
- 79. That’s what youwant to see!
- 80. There’s more thanone! Planning: Time: Registration / Sales:
- 81. I can showyou Everything! I just need to see: UNCONFIRMED CONFIRMED RUNNING PAST CANCELED
- 82. User Perceived StateMachine UNCONFIRMED CONFIRMED RUNNING PAST CANCELED
- 83. User Perceived StateMachine Sales Event Time Read Model Closed Unconfirmed Future Stealth Closed Confirmed Future Confirmed Closed Canceled Future Canceled Open Unconfirmed Future Unconfirmed Open Confirmed Future Confirmed Open Canceled Future Error Closed Unconfirmed Present Forgot something? Closed Confirmed Present Running Closed Canceled Present 😭😭😭😭😭😭😭 Open … Present Hey Wait a Minute! … … … …
- 84.
- 85.
- 86. I’ll couple everything togive you the state machine you want!
- 87.
- 89. Spice up yourmodels! Photo by Tamanna Rumee on Unsplash
- 91. Give yourself more thanone option
- 92. Add Layers toyour whirlpool!
- 93.
- 94. Digital Tools arechanging your brain priorities I enter a session to model, and I find myself aligning rectangles and making arrows clear.
- 95. Get Yourself aGreen Bar!
- 96. Combining Different Styles LittleCherry on top
- 97. A Scatter-Gather Style Design Planning Sales Inventory Logistics Tracking Training Summary Public Event Open Event Printables Venue Booking Ticket Sale Purchase State-Based Aggregates(or nobody cares about your intermediate events anyway) Structural composition and possible collaboration Specifications as warnings. Read Models on Steroids, focus on information readability and sense-making for the users. EventSourcing on multiple parallel axes: events are meaningful for the listeners Policies -> Sagas or Process Managers to allow business flexibility Draft Executable Tracking Possible upscale to state-driven style Title
- 98. Pick the righttool for the job
- 99. Maybe we canavoid it!
- 100. Lightweight Boundaries Postpone physicalseparation as long as you can. Make sure your team has enough discipline to support the logical separation.
- 101.
- 102. Biases and shortcutsare nudging you to repeat past errors
- 103. I’ll follow you everywheremy beloved domain expert!! Why don’t we just patch the legacy?
- 104. Sometimes we gottaPull! Photo by Ugur Arpaci on Unsplash
- 105. Design Integrity is YOURBUSINESS
- 106. Can’t outsource itto the Domain Expert
- 107. You Can StartClean Quick and Dirty is not the only option
- 108. Give yourself onemore alternatives Your 1st choice is probably unsafe
- 109. What is visible? Session Plan Ticket Plan Training Summary Schedule Public Event Ticket SaleOpen Event Session Type Session Session Duration Session Can Domain Experts help here?
- 110. What is visible? ReadModels Aggregates UI Not everything needs to be discussed in the same way Commands (Labels and Intentions) Commands Events Policies
- 111. Business Composability Is Business Confidence Butmake sure it comes from code, not from PowerPoints
- 112.
- 113.
- 114. 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 • http://blog.avanscoperta.it • Twitter: @ziobrando • Trainings & Workshop facilitation: info@avanscoperta.it • http://www.avanscoperta.it