Towards a Practical, Unified Dependability Measure for Dynamic Systems

Providing a practical measure of the dependability of dynamic systems, including software systems and components, has been an elusive goal of systems engineers for some time. Measures for static, individual, dependability-relevant properties (e.g. reliability, safety, availability etc.) are well understood, but to date there is no general and widely accepted way of combining these into a single dependability measure that can be used to assess a dynamic system’s capability for specific applications. In this paper we present a practical approach for obtaining an Integrated Dependability Measure (IDM) by placing the onus on system developers and users to capture the acceptability of different behavior in the form of acceptability functions rather than by defining (or attempting to define) general purpose combinations of separately determined dependability ingredients (e.g. reliability, safety etc.).