A New Formalism for Designing and Specifying RAMS Parameters for Complex Distributed Control Systems: The Safe-SADT Formalism

Abstract

Dependability evaluation is a fundamental step in distributed control system design. However, the current dependability evaluation methods are not appropriate due to the level of complexity of such systems. Given the ineffectiveness of these methods, we propose the Safe-SADT formalism for dependability evaluation (SADT stands for Structured Analysis and Design Techniques). This formalism allows the explicit formalization of functional interaction, the identification of the characteristic values affecting complex system dependability, the quantification of RAMS parameters (Reliability, Availability, Maintainability, and Safety) for the system's operational architecture, and the validation of the operational architecture in terms of the dependability objectives and constraints required by the functional specifications. The results presented in this paper are limited to RAMS quantification.