A new approach to modeling the system reliability: dynamic reliability block diagrams

Nowadays, also as consequence of recent chronicles, aspects like security, availability, reliability and other features of a generic system summarized under the concept of dependability are receiving increasing attention. This fact is translated into specific requirements as well as explicit and tighter constraints the system must satisfy. But sometimes, with particular reference to the reliability, there is lack of suitable tools to properly model, analyze and study in depth these aspects. To fill this gap, a new modeling tool is proposed, extending and enhancing the existing reliability block diagram (RBD) formalism: the dynamic RBD (DRBD). The DRBD permits to model the dynamic reliability behavior of a system through the proposed various dependencies models as well as redundancy and load sharing policies models. The flexible DRBD dependencies management is based on an articulated dynamic model composed by states and events. The capabilities, flexibility, and other features of the proposed new modeling approach are illustrated using the modeling of an example computer system. Different possible solution techniques are also discussed for a DRBD model: Markov chain, Petri nets, analytic, Monte Carlo simulation, and a modular approach which combines the classical analytic RBD solution and the dynamic solutions