Modeling Dependability of Dynamic Computing Systems

A trend actually characterizing any technological and application field is the use of control and computing devices. This moves the attention of the insiders on the management of more complex processes and systems, modifying requirements, tasks and skills. In this scenario the dependability evaluation becomes strategic. The increasing complexity of systems requires a serious revision of the techniques and the methodologies exploited for evaluating the system dependability. Notations as reliability block diagrams (RBD), fault trees (FT) or reliability graphs (RG) and their extensions, such as dynamic FT (DFT), could not adequately model dynamic reliability/availability aspects and behaviors as the units' interactions. To overcome those problems we developed a new formalism derived from RBD: the dynamic RBD (DRBD). DRBD allow to represent dynamic reliability/availability behaviors by specifying the dependency concept. The dependency is the building block for modeling dynamic aspects in DRBD. In this paper we detail the DRBD modeling technique thorough an example of distributed computing system taken from literature. By this we also compare our approach with the DFT one, providing proofs of the DRBD potentialities in dynamic reliability/availability