# Finite State Machine

> A conceptual representation of behavior as a closed set of states and the events that move between them.

Record: `architecture:finite-state-machine`
Kind: model
Layer: [Design Patterns Core](https://banes-lab.com/records/layer/design-patterns-core.md)
Severity: recommended
Scope: behavior, state modeling, control flow
Canonical: https://banes-lab.com/ontology#architecture-finite-state-machine

Listed in [Architecture principles](https://banes-lab.com/api/records/architecture.md), after [Null Object Pattern](https://banes-lab.com/records/architecture/null-object-pattern.md) and before [Statecharts](https://banes-lab.com/records/architecture/statecharts.md).

## Repair

- Refactored by: Model states and transitions as an explicit FSM
- Detected by: impossible or contradictory state combinations reachable at runtime
- Violated by: behavior driven by ad-hoc combinations of scattered status booleans
- Measured by: count of representable-but-illegal states
- Enforced by: state model review

## Requires

- [Explicit State Set](https://banes-lab.com/records/lexicon/explicit-state-set.md)

## Reinforces

- [State Pattern](https://banes-lab.com/records/architecture/state-pattern.md)
- [Correctness](https://banes-lab.com/records/architecture/correctness.md)

## Enables

- [Legal-Transition Enforcement](https://banes-lab.com/records/lexicon/legal-transition-enforcement.md)
- [Exhaustive State Reasoning](https://banes-lab.com/records/lexicon/exhaustive-state-reasoning.md)

## Conflicts with

- [Boolean Flag Soup](https://banes-lab.com/records/lexicon/boolean-flag-soup.md)

## In tension with

- [State Explosion](https://banes-lab.com/records/lexicon/state-explosion.md)

## Tensions

- [Finite State Machine / State Explosion](https://banes-lab.com/records/tension/finite-state-machine-state-explosion.md)

## Contracts

- [Finite State Machine](https://banes-lab.com/records/algorithms/finite-state-machine.md)

## Severity

- [recommended](https://banes-lab.com/records/vocabulary/severity-recommended.md)

## Category

- [Behavioral Patterns](https://banes-lab.com/records/architecture-category/behavioral-patterns.md)

## Required by

- [Statecharts](https://banes-lab.com/records/architecture/statecharts.md)

## Reinforced by

- [Statecharts](https://banes-lab.com/records/architecture/statecharts.md)

## Linked from

- [Orchestration as declared structure](https://banes-lab.com/pag/orchestration/declared-structure.md)
- [Correctness / Determinism / Verification](https://banes-lab.com/ontology/principles/architecture-category-correctness-determinism-verification.md)
- [Behavioral Patterns](https://banes-lab.com/ontology/principles/architecture-category-behavioral-patterns.md)
- [Behavioral Patterns](https://banes-lab.com/ontology/lexicon/lexicon-category-behavioral-patterns.md)
- [Core Vocabulary](https://banes-lab.com/ontology/lexicon/lexicon-category-core-vocabulary.md)
- [Architecture](https://banes-lab.com/ontology/algorithms/algorithms-domain-architecture.md)
- [Severity levels](https://banes-lab.com/ontology/schema/the-vocabulary-severity.md)
- [The resolutions](https://banes-lab.com/ontology/schema/the-resolutions.md)