stpa-step1-define-purpose

Defining the purpose in STPA involves identifying unacceptable losses, pinpointing system hazards that lead to those losses, and deriving system-level constraints to prevent them, establishing a clear safety baseline for complex systems.

You identify hazards by pinpointing system states that could lead to unacceptable losses, then derive constraints by creating rules the system must follow to prevent these hazards during your safety analysis.

You need to define losses and hazards before analyzing the safety of any complex system, such as an autonomous vehicle's braking system, to clearly document unacceptable outcomes and establish a foundational safety scope.

Yes, you can use this STPA method to analyze an autonomous vehicle's braking system by documenting losses like accidents, identifying hazards like uncommanded acceleration, and defining constraints like mandatory deceleration.

In STPA, a loss is an unacceptable outcome for the system, while a hazard is a specific system state or condition that could lead directly to that identified loss, requiring constraints to prevent it.