Confidence in System Safety

Safety is a property of Sociotechnical Systems not of software - We should set the system boundary where the dependence on assumptions is minimised and most certain • We should reduce functionality and use our best designers to make the system as simple as possible • We should • build safety cases from claims about system properties, not about rates of failures • rely on evidence from analysis where possible • use rigorous notations and automated analysis • We must develop standards that demand strong evidence for feasible claims • If an application needs a degree of dependability for which adequate confidence cannot be achieved before deployment, we must say "no"