Model states and valid transitions
Course overview · 4 min reading + 12 min practice, estimated
Principles and method
Write the states an item can occupy and the events that permit transitions. Include waiting, failed, cancelled and needs-review states rather than only success. Define invariants that must remain true, such as a withdrawn application cannot receive a new interview invitation. Check current state at the moment of action because events may arrive late or out of order. Use version checks where concurrent updates could overwrite each other. A state diagram should explain what happens when two systems disagree and which owner resolves the conflict.
Worked example
A candidate withdraws while an interview invitation is queued. The send step reads current application state and cancels the operation, even though the original scheduling event was valid.
Put it into practice
Draw a state machine for interview coordination with withdrawal and rescheduling.
Use fictional information and keep your work in your own notes.
Compare your approach: self-review guidance
List permitted transitions and one forbidden transition. Include a stale-event test. The diagram should prevent a past event from overriding a newer decision.
Sources and further reading
Original Academy teaching and fictional examples. These references provide context, not endorsement. Edition 2026.09; updated 2026-09-24.
- GOV.UK: Responsible AI in recruitment
UK guidance on procuring and deploying recruitment AI.
- NIST: AI Risk Management Framework
Voluntary framework for organising AI risks and controls.