A Subjective Logic-based method for runtime confidence updates in safety arguments
Traditional static safety cases struggle to dynamically respond to runtime evidence and cannot continuously quantify confidence in system safety. This work proposes a dynamic safety argumentation framework grounded in subjective logic, which integrates design-time evidence with runtime Safety Performance Indicators (SPIs). By employing a sliding window mechanism to process SPI data in real time, the framework introduces a confidence-updating rule prioritizing safety responsiveness—gradually increasing confidence in the absence of violations while imposing swift penalties upon detection of anomalies—thereby overcoming limitations inherent in conventional Bayesian posterior updating. The approach is validated through simulations of an assistive function in construction zones, effectively demonstrating the dynamic evolution of confidence in a machine learning–driven traffic cone detection component as informed by runtime evidence.