Measurement-Based Dependability Evaluation for Safety-Grade Digital Systems 1

This paper presents a measurement-based methodology for dependability 2 evaluation of safety-grade digital instrumentation and control (I&C) systems. This methodology uses failure data from operational systems to assess reliability and availability, to identify problem areas, and to determine the no-failure test duration required for achieving a certain level of dependability. The methodology is used with actual data from nuclear safety, nuclear control, and air traffic control systems to demonstrate an experimental approach to the objective evaluation of dependability for critical systems.