Safety, Liveness, and Information Flow: Dependability Revisited

Zinaida Benenson, Felix Freiling, Thorsten Holz, Dogan Kesdogan, Lucia Draque Penso

ARCS Workshop on Dependability and Fault-Tolerance, Frankfurt am Main, Germany, March 2006


Abstract

We present a formal framework to talk and reason about dependable systems. The framework is based on three distinct classes of (system specification) properties we call safety, liveness and information flow. We discuss several examples of dependable systems within this framework and argue that these classes are sufficient to model the functional requirements of dependable systems satisfying to high degrees both fault-tolerance and security attributes. The framework is meant to be a minimal security-specific extension of the asynchronous system model from fault-tolerant distributed algorithms and aimed to support teaching the concepts of fault-tolerance and security within a uniform system model. To remain minimal, the framework does not cover probabilistic or complexity theoretic aspects of dependability (like reliability or computational security).

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Tags: dependability