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55
Actions Speak Louder than Words: Proving Bisimilarity for ContextFree Processes
, 1997
"... Baeten, Bergstra, and Klop (and later Caucal) have proved the remarkable result that bisimulation equivalence is decidable for irredundant contextfree grammars. In this paper we provide a much simpler and much more direct proof of this result using a tableau decision method involving goaldirected ..."
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Cited by 47 (10 self)
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Baeten, Bergstra, and Klop (and later Caucal) have proved the remarkable result that bisimulation equivalence is decidable for irredundant contextfree grammars. In this paper we provide a much simpler and much more direct proof of this result using a tableau decision method involving goaldirected rules. The decision procedure also provides the essential part of the bisimulation relation between two processes which underlies their equivalence. We also show how to obtain a sound and complete sequentbased equational theory for such processes from the tableau system and how one can extract what Caucal calls a fundamental relation from a successful tableau.
Supervisory Control of Nondeterministic Systems with Driven Events via Prioritized Synchronization and Trajectory Models
 SIAM Journal of Control and Optimization
, 1995
"... We study the supervisory control of nondeterministic discrete event dynamical systems (DEDS's) with driven events in the setting of prioritized synchronization and trajectory models introduced by Heymann. Prioritized synchronization captures the notions of controllable, uncontrollable, and dri ..."
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Cited by 32 (9 self)
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We study the supervisory control of nondeterministic discrete event dynamical systems (DEDS's) with driven events in the setting of prioritized synchronization and trajectory models introduced by Heymann. Prioritized synchronization captures the notions of controllable, uncontrollable, and driven events in a natural way, and we use it for constructing supervisory controllers. The trajectory model is used for characterizing the behavior of nondeterministic DEDS's since it is a sufficiently detailed model (in contrast to the less detailed language or failures models), and serves as a language congruence with respect to the operation of prioritized synchronization. We obtain results concerning controllability and observability in this general setting. Keywords: discrete event systems, supervisory control, nondeterministic automata, driven events, prioritized synchronization, trajectory models AMS (MOS) subject classifications: 68Q75, 93B25, 93C83 1 Introduction Supervisory control o...
Iterating Transducers
, 2001
"... Regular languages have proved useful for the symbolic state exploration of infinite state systems. They can be used to represent infinite sets of system configurations; the transitional semantics of the system consequently can be modeled by finitestate transducers. A standard problem encountered ..."
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Cited by 32 (0 self)
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Regular languages have proved useful for the symbolic state exploration of infinite state systems. They can be used to represent infinite sets of system configurations; the transitional semantics of the system consequently can be modeled by finitestate transducers. A standard problem encountered when doing symbolic state exploration for infinite state systems is how to explore all states in a finite amount of time. When representing the onestep transition relation of a system by a finitestate transducer T , this problem boils down to finding an appropriate finitestate representation T for its transitive closure. In this
Correctness of Pipelined Machines
 Formal Methods in ComputerAided Design–FMCAD 2000, volume 1954 of LNCS
"... The correctness of pipelined machines is a subject that has been studied extensively. Most of the recent work has used variants of the Burch and Dill notion of correctness [4]. As new features are modeled, e.g., interrupts, new notions of correctness are developed. Given the plethora of correctness ..."
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Cited by 31 (13 self)
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The correctness of pipelined machines is a subject that has been studied extensively. Most of the recent work has used variants of the Burch and Dill notion of correctness [4]. As new features are modeled, e.g., interrupts, new notions of correctness are developed. Given the plethora of correctness conditions, the question arises: what is a reasonable notion of correctness? We discuss the issue at length and show, by mechanical proof, that variants of the Burch and Dill notion of correctness are awed. We propose a notion of correctness based on WEBs (Wellfounded Equivalence Bisimulations) [16, 19]. Briey, our notion of correctness implies that the ISA (Instruction Set Architecture) and MA (MicroArchitecture) machines have the same observable in nite paths, up to stuttering. This implies that the two machines satisfy the same CTL* X properties and the same safety and liveness properties (up to stuttering). To test the utility of the idea, we use ACL2 to verify s...
Bisimulation, Modal Logic and Model Checking Games
, 1999
"... We give a very brief introduction to how concurrent systems can be modelled within process calculi, as terms of an algebraic language whose behaviours are described using transitions. Reasoning has centred on two kinds of questions. One is relationships between descriptions of concurrent systems. Th ..."
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Cited by 25 (0 self)
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We give a very brief introduction to how concurrent systems can be modelled within process calculi, as terms of an algebraic language whose behaviours are described using transitions. Reasoning has centred on two kinds of questions. One is relationships between descriptions of concurrent systems. The other is appropriate logics for describing crucial properties of concurrent systems. Bisimulation equivalence is briefly described. It can also be characterised in terms of modal logic (HennessyMilner logic). However as a logic it is not very expressive. So we also describe modal mucalculus which is a very expressive temporal logic. In the main part of the paper we show that property checking can be understood in terms of game playing. In the finite state case, games underpin ecient model checking algorithms. The games are also denable independently of property checking as graph games which can be reduced to other combinatorial games.
A Gap Property of Deterministic Tree Languages
"... We show that a tree language recognized by a deterministic parity automaton is either hard for the coBüchi level and therefore cannot be recognized by a weak alternating automaton, or is on a very low level in the hierarchy of weak alternating automata. We also give a new simple proof of the strict ..."
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Cited by 22 (4 self)
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We show that a tree language recognized by a deterministic parity automaton is either hard for the coBüchi level and therefore cannot be recognized by a weak alternating automaton, or is on a very low level in the hierarchy of weak alternating automata. We also give a new simple proof of the strictness of the hierarchy of weak alternating automata.
Bisimulation Invariance and Finite Models
 IN LOGIC COLLOQUIUM ’02
, 2006
"... We study bisimulation invariance over finite structures. This investigation leads to a new, quite elementary proof of the van BenthemRosen characterisation of basic modal logic as the bisimulation invariant fragment of firstorder logic. The ramification of this characterisation for the finer no ..."
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Cited by 16 (3 self)
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We study bisimulation invariance over finite structures. This investigation leads to a new, quite elementary proof of the van BenthemRosen characterisation of basic modal logic as the bisimulation invariant fragment of firstorder logic. The ramification of this characterisation for the finer notion of global twoway bisimulation equivalence is based on bisimulation respecting constructions of models that recover in finite models some of the desirable properties of the usually in finite bisimilar unravellings.
Compositional abstractions of hybrid control systems
 In Proceedings of the 40th IEEE Conference on Decision and Control
, 2001
"... Abstract. Abstraction is a natural way to hierarchically decompose the analysis and design of hybrid systems. Given a hybrid control system and some desired properties, one extracts an abstracted system while preserving the properties of interest. Abstractions of purely discrete systems is a mature ..."
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Cited by 14 (1 self)
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Abstract. Abstraction is a natural way to hierarchically decompose the analysis and design of hybrid systems. Given a hybrid control system and some desired properties, one extracts an abstracted system while preserving the properties of interest. Abstractions of purely discrete systems is a mature area, whereas abstractions of continuous systems is a recent activity. In this paper we present a framework for abstraction that applies to discrete, continuous, and hybrid systems. We introduce a composition operator that allows to build complex hybrid systems from simpler ones and show compatibility between abstractions and this compositional operator. Besides unifying the existing methodologies we also propose constructions to obtain abstractions of hybrid control systems.
Tile Bisimilarity Congruences for Open Terms and Term Graphs
 in: Proc. CONCUR 2000, LNCS 1877 (2000
, 2000
"... The definition of sos formats ensuring that bisimilarity on closed terms is a congruence has received much attention in the last two decades. For dealing with open system specifications, the congruence is usually lifted from closed terms to open terms by instantiating the free variables in all possi ..."
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Cited by 13 (7 self)
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The definition of sos formats ensuring that bisimilarity on closed terms is a congruence has received much attention in the last two decades. For dealing with open system specifications, the congruence is usually lifted from closed terms to open terms by instantiating the free variables in all possible ways; the only alternatives considered in the literature relying on Larsen and Xinxin's context systems and Rensink's conditional transition systems. We propose a different approach based on tile logic, where both closed and open terms are managed analogously. In particular, we analyze the `bisimilarity as congruence' property for several tile formats that accomplish di erent concepts of subterm sharing.