Specification and Analysis of Fault Behaviours Using Graph Grammars

In this paper we make use of formal methods and tools as means to specify and reason about the behavior of distributed systems in the presence of faults. The approach used is based on the observation that a fault behavior can be modeled as an unwanted but possible transition of a system. It is then possible to define a transformation of a model M1 of a distributed system into a model M2 representing the behavior of the original system in the presence of a selected fault. We use a formal specification language called Object Based Graph Grammars to describe models of asynchronous distributed systems and present, for models written in terms of this language, the transformation steps for introducing a set of classical fault models found in the literature. As a result of this process, over the transformed model(s) it is possible for the developer to reason about the behavior of the original model(s) in the presence of a selected fault behavior. As a case study, we present the specification of a pull-based failure detector, then we transform this model to include the behavior of the crash fault model and analyze, through simulation, the behavior of the pull-based failure detector in the presence of a crash.