Structure Keywords

Keywords for defining machines, systems, and scenarios.

machine:

Defines a machine template (actor) in the system.

machine: @order

The machine name must be prefixed with @.

Template vs Instance

A machine: definition is a template. At runtime, instances (aggregates) are created from this template when events arrive:

• First event → creates new instance with unique ID (e.g., @order:abc123)
• Subsequent events → route to existing instances via conversation context

See Instance Management for details on how instances are created and routed.

system:

Defines a multi-machine system.

system: e-commerce checkout

scenario:

Defines a feature or capability of a machine.

scenario: checkout flow

A scenario groups related event handlers together.

uses:

Imports machines into a system from separate files.

system: checkout

uses:
  @order from "./order.flow"
  @payment from "./payment.flow"