Community: Glossary of State Machine Terms

A living glossary of important state machine, statechart, and actor model concepts.

Terms

A condition or mode a system can be in. In UI, examples include loading, idle, error, editing.

Something that happens, usually triggered by the user or system. Events ask the machine to transition.

A change from one state to another in response to an event.

A condition that must be true for a transition to occur. Also known as a conditional transition.

A side effect that occurs as part of a transition, such as sending a request or updating context.

An entity that can receive and send events, and can spawn child actors. In XState v5, every interpreted machine is an actor.

Creating a new actor from within an existing actor.

Calling a service (promise, callback, observable, or another machine) from within a state.

A state that contains multiple orthogonal regions that are active simultaneously.

A pseudo-state that remembers the previous active sub-state when re-entering a compound state.

Extended state data associated with a machine, separate from the finite state value.

A finite state machine — defined by states, events, transitions, and initial state.

An extended state machine formalism that adds hierarchy, parallelism, and history.

Add diagrams for each term

Add code examples for each concept

Add links to relevant articles