Why it matters
State machines are useful when behavior matters: startup, shutdown, fault handling, maintenance, degraded modes, autonomous operation, or mission phases.
What is a state machine?
A state machine models system behavior as states and transitions, often including triggers, guards, actions, and operating modes.
State machine
A state machine models how a system behaves over time. It describes the states a system can be in and the transitions that move it from one state to another. In engineering systems, transitions often include triggers, guard conditions, actions, and timing assumptions.
Common mistakes
- Leaving behavior in prose while architecture looks complete
- Modeling normal operation but not fault or recovery states
- Drawing state diagrams that are not connected to requirements or verification plans
Where this concept fits in Cairn
Cairn models states and transitions as structured artifacts attached to model nodes. That keeps behavior connected to the subsystem it describes, alongside requirements, interfaces, and verification plans.
FAQ
When should a team use a state machine?
Use a state machine when the system has meaningful modes, transitions, fault handling, operating phases, or behavior that needs to be reviewed.
Can state machines connect to requirements?
Yes. In a structured model, behavior can be linked to requirements, interfaces, and verification records.