Event Modeling building block (the 'automation slice') that acts as a process orchestrator between autonomous modules that don't know of each other. Conceptually a robot that listens for events and keeps a to-do list of commands to dispatch when certain events occur, serving as the glue between modules. May be stateless (simple case: on event X send command Y) or stateful (holding at minimum a cursor into the event store, or full process state when multiple events must align before issuing a command — in which case a saga is typically introduced and may produce artificial intermediate events).