On bisimulation, fault-monotonicity and provable fault-tolerance

Abstract

We introduce a necessary test for the claims about provable fault-tolerance: having proved to tolerate several faults, we must tolerate (provably) any combination of them. One notable failure to pass this test is bisimulation. The paper presents a class of bisimulations which are fault-monotonic and within CCS support compositional design of component specifications by stepwise refinement, each step increasing or at least preserving the current level of fault-tolerance.

Synthesizing fault-tolerant programs from deontic logic specifications

“…Riely and Hennessy [Riely and Hennessy, 1997] use process algebra to describe a model of locations and failures providing a number of semantic equivalences. Janowski in [Janowski, 1995[Janowski, , 1997, investigated various notions of bisimulation with the aim of capturing fault-tolerant properties, in a CCSbased approach. In addition, these approaches have been applied to several case studies.…”

“…Additionally, we mention the work presented in [Janowski, 1995[Janowski, , 1997, where various notions of bisimulation are investigated with the aim of capturing fault-tolerant properties, in the context of process algebras. An obvious difference with respect to our work is that we use a state based approach and a temporal logic to reason about state based models, in contrast to the aforementioned works where process algebras are employed for modeling systems, and the associated logic is a variation of Hennesy-Milner logic, which is known to be less expressive than temporal logics.…”

“…Some examples are the use of program transformation [Kulkarni and Arora, 2000;Ebnenasir, 2003, 2004;Ebnenasir et al, 2008;Bonakdarpour et al, 2012], process algebra based approaches [Janowski, 1995[Janowski, , 1997, specification languages (e.g., Alloy [Kang and Jackson, 2008], TLA+ [Lamport and Merz, 1994], and Event-B [Yadav and Butler, 2009]), etc. Related to the last, recently some researchers (e.g., [Carmo and Jones, 1996a;Khosla and Maibaum, 1987;Kent et al, 1991;Khosla, 1989;Lomuscio and Sergot, 2004;Fiadeiro and Maibaum, 1991]) have pointed out that deontic logic, a variation of logic advocated for the study of norms, is useful for reasoning about fault-tolerant systems.…”

Self-Similarity Breeds Resilience

“…The idea of formulating fault tolerance in terms of behavioural equivalence is not new [14,17,11]. The idea of a fault preorder, capturing the relative severity of faults, can be found in the works of Janowski, Krishnan and others [11,12,14]. Janowski, e.g., studies the problem of monotonicity of fault tolerance -a system tolerant of faults higher in the preorder should tolerate faults lower in the preorder, but finds that this requirement does not square well with the standard notion of bisimilarity.…”

“…Another major difference with these approaches [10,11] is that they formulate the faulty versions of the system by incorporating the anticipated faulty behaviour into definitions of the system. We see this is as unsatisfactory in that the adversarial behaviour has to be expressed concretely and within the syntax of the system (e.g., in the CCS formulation), thereby severely restricting the expressive power given to the adversary.…”