DDD Vienna 2018: Event storming! Putting it all together.

Event Storming Workshop, DDD Vienna Meetup, March 23rd 2018

Transcript

1. Event storming! Putting it all together. @martinschimak -> March 23rd, 2018 -> Domain-Driven Design Vienna
2. The credit is due to him.
3. Event storming starts with brainstorming events. Goods shipped Order placed Goods fetched Payment received „We need to create a set of facts to create value for customers!“
4. Events are just that: facts Something happened! Now it‘s in the past. And therefore in the past tense! Payment received
5. Somebody needs to create the facts Nothing „really“ happened so far! Apart from that we intend to create new facts! :-) Request payment
6. Commands are intent Request payment
7. Now it happened! New facts we can build upon. Payment received Request payment
8. First, start with some of the facts… Goods shipped Order placed Goods fetched Payment received Order fulfilled
9. … then add some commands as appropriate Goods shipped Order placed Goods fetched Payment received Place order Request payment Fetch goods Ship goods Order fulfilled
10. Some commands might be triggered by users… Goods shipped Order placed Goods fetched Payment received Place order Request payment Fetch goods Ship goods Order fulfilled
11. …whereas others happen because of internal policies Goods shipped Order placed Goods fetched Payment received Place order Request payment Fetch goods Ship goods Order fulfilled Policy
12. Policies sit in between events and commands If this then that! Order placed Request payment The simplest possible policy is that whenever an event happens, we always follow up with a command
13. Use policies to indicate the more interesting stuff! Order placed Place order Order fulfilled Goods fetched Fetch goods Payment received Request payment Optionally wait for payment Ship goods Goods shipped When shipped and paid Mark order fulfilled
14. You might want to indicate external systems Order placed Place order Order fulfilled Goods fetched Fetch goods Payment received Request payment Optionally wait for payment Ship goods Goods shipped When shipped and paid Mark order fulfilled Inventory system
15. Pro Tip: don‘t fall in love with your (own) sticky notes!
16. When you don‘t like some stuff schedule it for removal Order placed Place order Order fulfilled Goods fetched Fetch goods Payment received Request payment Optionally wait for payment Ship goods Goods shipped When shipped and paid Mark order fulfilled Coffee brewed
17. Domain Event To sum it up. It starts with some events.
18. Domain Event We add some commands Command Command
19. Domain Event Optionally we show that a command is triggered by a user Command Command
20. Domain Event Optionally we show a specific policy triggering a command Command Command (Optional) Policy
21. Domain Event (Optional) Policy Command Command Optionally we show a command is invoked on external systems (Optional via) External System
22. Now have fun!
23. Domain Event (Optional) Policy Command Command Our legend for today. We never (ever) use arrows! :-) (Optional via) External System
24. Read Model Domain Event Aggregate Policy Command External System UI Command Invoked on raises raises Invoked on projected onto listened to by triggers triggers Inspired by the picture that explains (almost) everything :-) * *) Idea: the ingenious Alberto Brandolini
25. Event Storming Master Class?
26. Brussels APRIL 11-13, 2018 Advanced Domain–Driven Design MATHIAS VERRAES APRIL 12-13, 2018 EventStorming Master Class ALBERTO BRANDOLINI Paris MAY 24-25, 2018 Essential Domain–Driven Design PAUL RAYNER JUNE 26-29, 2018 DDD Immersion ERIC EVANS