event-modeling

STARTER_CHARACTER = 🗺️

What Event Modeling Produces

A set of vertical slices that fully describe a system's behavior. Each slice is independently implementable and testable. The model uses business language throughout — no infrastructure or technical terms.

                    ┌─────────────────────────────────────┐
                    │          Event Model                │
                    │                                     │
                    │  ┌───────────┐  ┌───────────┐       │
                    │  │  Slice 1  │  │  Slice 2  │  ...  │
                    │  │ STATE_    │  │ STATE_    │       │
                    │  │ CHANGE    │  │ VIEW      │       │
                    │  └───────────┘  └───────────┘       │
                    │         │              ▲            │
                    │         │  (events)    │            │
                    │         └──────────────┘            │
                    └─────────────────────────────────────┘

Slice Types

Three types. Every behavior in the system fits one:

STATE_CHANGE — user does something

• Screen → Command → Event
• Command produces one or more events
• May have error events for failure paths

STATE_VIEW — system shows something

• Events → Read Model → Screen
• Read model aggregates data from one or more events

AUTOMATION — system reacts to something

• Event → Processor → Command → Event
• Background process, no user interaction

See references/slice-types.md for element rules, dependency patterns, and naming conventions.

Conversational Design Process

Work with the user through these phases. Move at the user's pace — they might want to go deep on one slice before seeing the full picture.

Phase 1: Understand the Domain

Identify aggregates (core business entities), actors, and high-level use cases. Ask about the business processes, not technical implementation.

Phase 2: High-Level Model

Draft all slices without field details. Show the flow between them — which events feed which read models, which screens lead to which commands. This is the "map" of the system.