Tod Courtney

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The Möbius framework is an environment for supporting multiple modeling formalisms and solution techniques. Models expressed in formalisms that are compatible with the framework are translated into equivalent models using Möbius framework components. This translation preserves the structure of the models, allowing efficient solutions. The framework is(More)
Despite the development of many modeling formalisms and model solution methods, most tool implementations support only a single formalism. Furthermore, models expressed in the chosen formalism cannot be combined with models expressed in other formalisms. This monolithic approach both limits the usefulness of such tools to practitioners, and hampers modeling(More)
Building dependable distributed systems from commercial off-the-shelf components is of growing practical importance. For both cost and production reasons, there is interest in approaches and architectures that facilitate building such systems. The AQuA architecture is one such approach; its goal is to provide adaptive fault tolerance to CORBA applications(More)
Möbius 2.3 is an extensible dependability, security, and performance modeling environment for large-scale discrete-event systems. It provides multiple model formalisms and solution techniques, facilitating the representation of each part of a system in the formalism that is most appropriate for it, and the application of the solution method or(More)
The Möbius modeling tool provides an infrastructure to support multiple interacting formalisms and solvers, and is extensible in that new formalisms and solvers can be added to the tool in such a way that they can interact with those already implemented without requiring additional changes to the previously implemented ones. We have continued to add(More)
MOTIVATION The stochastic kinetics of a well-mixed chemical system, governed by the chemical Master equation, can be simulated using the exact methods of Gillespie. However, these methods do not scale well as systems become more complex and larger models are built to include reactions with widely varying rates, since the computational burden of simulation(More)
Viruses that infect smartphones are emerging as a new front in the fight against computer viruses. In this paper, we model the propagation of mobile phone viruses in order to study their impact on the dependability of mobile phones. We propose response mechanisms and use the models to obtain insight on the effectiveness of these virus mitigation techniques.(More)
Despite the development of many modeling formalisms and model solution methods, most tool implementations support only a single formalism. Furthermore, models expressed in a chosen formalism cannot be combined to interact with models expressed in other formalisms. This chapter provides an overview of selected performance/dependability modeling tools(More)
An increasing number of computer systems are designed to be distributed across both local and wide-area networks, performing a multitude of critical information-sharing and computational tasks. Malicious attacks on such systems are a growing concern, where attackers typically seek to degrade quality of service by intrusions that exploit vulnerabilities in(More)