Safety Engineering Foundations
Derive constraints that prevent unacceptable losses, including losses from interactions between functioning components. Scope the analysis to the requested system and decision; analysis does not authorize external actions.
When to use
Use when a task requests hazard analysis, STPA, unsafe control actions, system safety constraints, or an evidence argument connecting controls to prevention of specified losses.
For failure rates, repair/availability models, FMEA, and fault-tree probabilities, use reliability theory. For proving specified model properties, use formal methods. Operational incident response and security hardening remain with their existing owners.
Quick Reference
Hazard analysis → STPA reference; completion claims → assurance reference; deliverable → traceability worksheet.
Workflow
- Define system boundary, stakeholders, lifecycle phase, unacceptable losses, and environmental assumptions. Separate an accident/loss from a hazardous system state.
- Model controllers, controlled processes, control actions, feedback, and process-model assumptions. Include humans and interacting controllers when relevant.
- Read STPA analysis and examine each action in four categories: omission, unsafe provision, timing/order, and inappropriate duration where applicable.
- For each unsafe control action (UCA), identify context and hazard; derive a testable constraint and assign an owner. Explore stale/missing feedback, flawed process models, conflicting commands, and unsafe execution paths, including functioning components.
- Fill the traceability worksheet. Read assurance and boundaries before making completion or safety claims. Use the synthetic example as an illustration, not a risk estimate.
Completion criteria
Every analyzed UCA links to a hazard and loss, a constraint, and planned or observed verification. Record excluded scenarios, unknowns, residual hazards, owners, and review triggers. A scenario with no test evidence remains a proposed mitigation.
Do not equate uptime with safety, assign fabricated event probabilities, or describe an STPA diagram as proof. This skill provides analysis and assurance structure; it does not certify compliance, establish acceptable risk, or grant approval authority. Respect authorization already supplied and identify any specific additional action requiring authorization without creating universal approval loops.
Fact-Checking
Use the dated primary source for method claims and system-specific evidence for effectiveness claims. Keep synthetic scenarios separate from observed incidents. Verify later method or system changes before describing them as current.
Navigation
- STPA analysis — four categories and loss-scenario derivation.
- Assurance and boundaries — evidence and limits.
- Completed example — synthetic rollback interaction.
- Traceability worksheet — output artifact.
- Dated primary sources — verified source and cutoff.