Documents

A flow is what d2 does when something happens: a message comes in, the rules that handle it run, and each can send more messages. Here most flows start from changes to th

NorthConf, a made-up two-day tech conference, as a domain model: the event and its venue, the programme, the people, tickets, and what happens on the day. Its sample data

Every day before the event (a cron, declared in Init): unpaid registrations get a reminder; on the day before, every volunteer gets their shifts.

Every message the event sends goes through this one rule, and here it's kept in the outbox (a Message object). In your own project, this is the one place to change for re

Check-in. A check-in at the door marks the registration as attended; a check-in into a session counts towards its room, and when a session has more people than its room h

The double-booking guard. Two sessions can't share a room at the same time. When a session is made or moved, this checks it against the other sessions in the same room: a

A new registration. The organizers hear who registered; the ticket type and the event count it (the event's seatsLeft follows), and when it reaches its capacity it's mark

Each of the event's flows, run by hand on the sample data (in the [Fiddle](/fiddle?tab=stories&topic=Story:events-flows), nothing is kept). The triggers in Init start the

Sample objects for events: NorthConf 2026, two days at the Harbourside Centre, 4 rooms, 3 tracks, 20 sessions, 10 speakers, 40 attendees with their registrations (paid, p