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Fair Simulation
 Information and Computation
, 1997
"... The simulation preorder for labeled transition systems is defined locally as a game that relates states with their immediate successor states. Simulation enjoys many appealing properties. First, simulation has a fully abstract semantics: system S simulates system I iff every computation tree embedd ..."
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Cited by 47 (17 self)
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The simulation preorder for labeled transition systems is defined locally as a game that relates states with their immediate successor states. Simulation enjoys many appealing properties. First, simulation has a fully abstract semantics: system S simulates system I iff every computation tree embedded in the unrolling of I can be embedded also in the unrolling of S. Second, simulation has a logical characterization: S simulates I iff every universal branchingtime formula satisfied by S is satisfied also by I. It follows that simulation is a suitable notion of implementation, and it is the coarsest abstraction of a system that preserves universal branchingtime properties. Third, based on its local definition, simulation between finitestate systems can be checked in polynomial time. Finally, simulation implies tracecontainment, which cannot be defined locally and requires polynomial space for verification. Hence simulation is widely used both in manual and in automatic verification. ...
Composition and Refinement of Discrete RealTime Systems
, 1998
"... Reactive systems exhibit ongoing, possibly nonterminating, interaction with the environment. Realtime systems are reactive systems that must satisfy quantitative timing constraints. This paper presents a structured compositional design method for discrete realtime systems that can be used to comb ..."
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Cited by 11 (2 self)
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Reactive systems exhibit ongoing, possibly nonterminating, interaction with the environment. Realtime systems are reactive systems that must satisfy quantitative timing constraints. This paper presents a structured compositional design method for discrete realtime systems that can be used to combat the combinatorial explosion of states in the verification of large systems. A composition rule describes how the correctness of the system can be determined from the correctness of its modules, without knowledge of their internal structure. The advantage of compositional verification is clear. Each module is both simpler and smaller than the system itself. Composition requires the use of both modelchecking and deductive techniques. A refinement rule guarantees that specifications of highlevel modules are preserved by their implementations. The StateTime toolset is used to automate parts of compositional designs using a combination of modelchecking and simulation. The design method is illustrated using a reactor shutdown system that cannot be verified using the StateTime toolset (due to the combinatorial explosion of states) without compositional reasoning. The reactor example also illustrates the use of the refinement rule.
The Essence of Coin Lemmas
 In Baier et al. [BHKR98
, 1998
"... Coin lemmas are one of the tools for the analysis of randomized distributed algorithms. Their principal role is to reduce the analysis of a randomized system to the analysis of an ordinary nondeterministic system. This paper describes the main ideas behind the formulation and use of coin lemmas and ..."
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Cited by 2 (0 self)
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Coin lemmas are one of the tools for the analysis of randomized distributed algorithms. Their principal role is to reduce the analysis of a randomized system to the analysis of an ordinary nondeterministic system. This paper describes the main ideas behind the formulation and use of coin lemmas and gives examples of coin lemmas of increasing complexity and generality. 1 Introduction Coin lemmas [8, 10, 11] are one of the existing tools for the analysis of randomized distributed algorithms. An algorithm is modeled as a probabilistic automaton, a labeled transition system whose transitions lead to probability distributions over states rather than to single states; a computation of an algorithm is modeled as a probabilistic execution, a cyclefree Markov chain obtained by unfolding the transition relation of the algorithm and by choosing a single transition at each point of the unfolding. The operation of choosing one transition at each point of the unfolding is called resolution of nond...