A Subjective Logic-based method for runtime confidence updates in safety arguments
For safety-critical autonomous systems, this method provides a practical way to dynamically update assurance confidence at runtime, balancing responsiveness and computational simplicity.
The paper presents a Subjective Logic-based method for runtime confidence updates in safety arguments, integrating design-time evidence and runtime safety performance indicators. Demonstrated on an ML-based construction cone detection system, it shows how confidence evolves with observed violations.
We present a method for dynamic quantitative assurance that enhances static safety cases with continuous, runtime-driven confidence updates. The method quantifies and propagates confidence across the development lifecycle by integrating design-time evidence and windowed runtime Safety Performance Indicators (SPIs) within a single Subjective Logic (SL)-based assurance case. At runtime, SPI evidence is continuously evaluated, and targeted claims are updated using a rule that increases confidence in the absence of violations and imposes prompt penalties when violations occur. This design prioritizes safety-relevant responsiveness over exact classical Bayesian posterior updates. We demonstrate the method using a simulation-based construction zone assist function, focusing on an ML-based construction cone detection component, and show how confidence evolves as SPI evidence is observed in operation.