this paper, we formally specify and verify the correctness of rollback relaxation. The problem is specified using the PVS Specification Language and proved using the PVS Prover. 1 Introduction Discrete event simulation is a key tool for system design and analysis. As systems grow in complexity, the need for higher throughput of discrete event simulators has increased. This has led to the development of techniques for parallel simulation and to the emergence of distributed synchronization algorithms for parallel simulation [4, 13]. Two approaches to distributed synchronization exist: conservative [13,18], and optimistic [2, 9]. In conservative approaches, the

Discrete-event simulation (DES) is a valuable design tool for several problems in engineering, computer science, economics and military applications. As many of these applications require enormous resources, parallel discrete-event simulation (PDES) is of considerable interest. Several parallel discrete-event simulation algorithms with different attributes have been reported in the literature [8]. This is due to the availability of several simulation paradigms with an assortment of optimizations. Parallel discrete-event

. Parallel and distributed systems are representative of large and complex systems that require the application of formal methods. These systems are often unreliable because implementors design and develop these systems without a complete understanding of the problem domain; in addition, the nondeterministic nature of certain parallel and distributed systems make system validation difficult if not impossible. To address this issue, the application of formal specification and verification to a class of parallel and distributed software systems is presented in this paper. Specifically, the Prototype Verification System (PVS) is applied to the specification and verification of the Time Warp protocol, a distributed optimistic discrete event simulation algorithm. The paper discusses how the specification of the Time Warp protocol can be mechanized within a general-purpose higher-order theorem proving framework like PVS. In addition, the paper presents the extensibility of the specification ...

With the advent of standardization efforts such as the High Level Architecture (HLA) and Distributed Interactive Simulation (DIS), inter-operability of military simulation models has emerged as the chief design requirement. By enforcing strict conformance to the DIS and/or HLA, the Defense Modeling and Simulation Office (DMSO) has so far been able to "mix-and-match" different simulation models and frameworks to satisfy the military's simulation needs. However, by linking different legacy simulations (simulations previously designed to operate independently) together, the simulation now has to correctly handle multiple levels of detail in the interacting simulation entities. In addition, a given entity itself can be represented in different ways each with a different level of detail (also referred to as resolution or fidelity). A natural question to ask in this situation is why does the model require different resolutions? Why isn't one level of resolution sufficient to address all the ...