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167
An Improvement of McMillan's Unfolding Algorithm
 Formal Methods in System Design
, 1996
"... McMillan has recently proposed a new technique to avoid the state explosion problem in the verification of systems modelled with finitestate Petri nets. The technique requires to construct a finite initial part of the unfolding of the net. McMillan's algorithm for this task may yield initial p ..."
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Cited by 203 (10 self)
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McMillan has recently proposed a new technique to avoid the state explosion problem in the verification of systems modelled with finitestate Petri nets. The technique requires to construct a finite initial part of the unfolding of the net. McMillan's algorithm for this task may yield initial parts that are larger than necessary (exponentially larger in the worst case). We present a refinement of the algorithm which overcomes this problem. 1 Introduction In a seminal paper [10], McMillan has proposed a new technique to avoid the state explosion problem in the verification of systems modelled with finitestate Petri nets. The technique is based on the concept of net unfolding, a well known partial order semantics of Petri nets introduced in [12], and later described in more detail in [4] under the name of branching processes. The unfolding of a net is another net, usually infinite but with a simpler structure. McMillan proposes an algorithm for the construction of a finite initial part...
Model Checking of Safety Properties
, 1999
"... Of special interest in formal verification are safety properties, which assert that the system always stays within some allowed region. Proof rules for the verification of safety properties have been developed in the proofbased approach to verification, making verification of safety properties simp ..."
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Cited by 136 (20 self)
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Of special interest in formal verification are safety properties, which assert that the system always stays within some allowed region. Proof rules for the verification of safety properties have been developed in the proofbased approach to verification, making verification of safety properties simpler than verification of general properties. In this paper we consider model checking of safety properties. A computation that violates a general linear property reaches a bad cycle, which witnesses the violation of the property. Accordingly, current methods and tools for model checking of linear properties are based on a search for bad cycles. A symbolic implementation of such a search involves the calculation of a nested fixedpoint expression over the system's state space, and is often impossible. Every computation that violates a safety property has a finite prefix along which the property is violated. We use this fact in order to base model checking of safety properties on a search for ...
Diagnosis of Asynchronous Discrete Event Systems, a Net Unfolding Approach
 IEEE TRANS. ON AUTOMATIC CONTROL
, 2001
"... In this paper we formulate asynchronous diagnosis by means of hidden state history reconstruction, from alarm observations. We follow a socalled true concurrency approach, in which no global state and no global time is available. Instead, we use only local states in combination with a partial order ..."
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Cited by 91 (28 self)
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In this paper we formulate asynchronous diagnosis by means of hidden state history reconstruction, from alarm observations. We follow a socalled true concurrency approach, in which no global state and no global time is available. Instead, we use only local states in combination with a partial order model of time, in which local events are ordered if they are either generated on the same site, or related via some causality relation. Our basic mathematical tool is that of net unfoldings originating from the Petri net research area. This study was motivated by the problem of event correlation in telecommunications network management.
Symbolic Verification with Periodic Sets
, 1994
"... Symbolic approaches attack the state explosion problem by introducing implicit representations that allow the simultaneous manipulation of large sets of states. The most commonly used representation in this context is the Binary Decision Diagram (BDD). This paper takes the point of view that other s ..."
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Cited by 78 (6 self)
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Symbolic approaches attack the state explosion problem by introducing implicit representations that allow the simultaneous manipulation of large sets of states. The most commonly used representation in this context is the Binary Decision Diagram (BDD). This paper takes the point of view that other structures than BDD's can be useful for representing sets of values, and that combining implicit and explicit representations can be fruitful. It introduces a representation of complex periodic sets of integer values, shows how this representation can be manipulated, and describes its application to the statespace exploration of protocols. Preliminary experimental results indicate that the method can dramatically reduce the resources required for statespace exploration.
Reliable Hashing without Collision Detection
 IN COMPUTER AIDED VERIFICATION. 5TH INTERNATIONAL CONFERENCE
, 1993
"... Thanks to a variety of new techniques, statespace exploration is becoming an increasingly effective method for the verification of concurrent programs. One of these techniques, hashing without collision detection, was proposed by Holzmann as a waytovastly reduce the amount of memory needed to s ..."
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Cited by 73 (1 self)
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Thanks to a variety of new techniques, statespace exploration is becoming an increasingly effective method for the verification of concurrent programs. One of these techniques, hashing without collision detection, was proposed by Holzmann as a waytovastly reduce the amount of memory needed to store the explored state space. Unfortunately, this reduction in memory use comes at the price of a high probability of ignoring part of the state space and hence of missing existing errors. In this paper, we carefully analyze this method and show that, by using a modified strategy, it is possible to reduce the risk of error to a negligible amount while maintaining the memory use advantage of Holzmann's technique. Our proposed strategy has been implemented and we describe experiments that confirm the excellent expected results.
Complexity Results for 1safe Nets
, 1993
"... We study the complexity of several standard problems for 1safe Petri nets and some of its subclasses. We prove that reachability, liveness, and deadlock are all PSPACEcomplete for 1safe nets. We also prove that deadlock is NPcomplete for freechoice nets and for 1safe freechoice nets. Finally, ..."
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Cited by 48 (7 self)
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We study the complexity of several standard problems for 1safe Petri nets and some of its subclasses. We prove that reachability, liveness, and deadlock are all PSPACEcomplete for 1safe nets. We also prove that deadlock is NPcomplete for freechoice nets and for 1safe freechoice nets. Finally, we prove that for arbitrary Petri nets, deadlock is equivalent to reachability and liveness. This paper is to be presented at FST&TCS 13, Foundations of Software Technology & Theoretical Computer Science, to be held 1517 December 1993, in Bombay, India. A version of the paper with most proofs omitted is to appear in the proceedings. 1 Introduction Petri nets are one of the oldest and most studied formalisms for the investigation of concurrency [33]. Shortly after the birth of complexity theory, Jones, Landweber, and Lien studied in their classical paper [24] the complexity of several fundamental problems for Place/Transition nets (called in [24] just Petri nets). Some years later, Howell,...
Deadlock Checking Using Net Unfoldings
 In Proceeding of 9th International Conference on Computer Aided Verification (CAV’97
, 1997
"... McMillan presented a deadlock detection technique based on unfoldings of Petri net systems. It is realized by means of a backtracking algorithm that has its drawback for unfoldings that increase widely. We present an approach that exploits precisely this property. Moreover, we introduce a fast imple ..."
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Cited by 40 (1 self)
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McMillan presented a deadlock detection technique based on unfoldings of Petri net systems. It is realized by means of a backtracking algorithm that has its drawback for unfoldings that increase widely. We present an approach that exploits precisely this property. Moreover, we introduce a fast implementation of McMillan's algorithm and compare it with our new technique. 1 Introduction In the field of static analysis of concurrent systems deadlock freeness is almost always a desirable property. Many research has been carried out to propose methods that check this property [3]. One of these was presented by McMillan in [8]. It is based on net unfoldings of Petri net systems. A net unfolding is class of partial order semantics of Petri nets, also known as branching process [4]. The heuristic used in McMillan's algorithm is particularly good where the unfolding grows more deeply than widely and thereby only few end points of the unfolding (i.e., cutoff points) have to be considered. The...
Distributed monitoring of concurrent and asynchronous systems
, 2005
"... In this paper we study the diagnosis of distributed asynchronous systems with concurrency. Diagnosis is performed by a peertopeer distributed architecture of supervisors. Our approach relies on Petri net unfoldings and event structures, as means to manipulate trajectories of systems with concurre ..."
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Cited by 40 (17 self)
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In this paper we study the diagnosis of distributed asynchronous systems with concurrency. Diagnosis is performed by a peertopeer distributed architecture of supervisors. Our approach relies on Petri net unfoldings and event structures, as means to manipulate trajectories of systems with concurrency. This article is an extended version of the paper with same title, which appeared as a plenary address in the Proceedings of CONCUR’2003.
The PEP Tool
, 1997
"... The PEP tool is a Programming Environment based on Petri Nets. Comprehensive modelling, compilation, simulation and verification components are embedded in a userfriendly graphical interface. The basic idea is that the modelling component allows the user to design parallel systems by parallel finit ..."
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Cited by 38 (2 self)
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The PEP tool is a Programming Environment based on Petri Nets. Comprehensive modelling, compilation, simulation and verification components are embedded in a userfriendly graphical interface. The basic idea is that the modelling component allows the user to design parallel systems by parallel finite automata, parallel programs, process algebra terms, highlevel or lowlevel Petri nets, and that the PEP system then automatically generates Petri nets from such models in order to use Petri net theory for simulation and verification purposes. This paper describes the typical usage of the PEP tool by considering the design of the wellknown `alternatingbit' protocol. Among others, the usefulness of new concepts for the handling of hierarchies and synchronous communication is explained. PEP has been implemented on Solaris 2.x, SunOS 4.1.x and Linux. Ftpable versions are available via http://www.informatik.unihildesheim.de/¸pep. Keywords: `Alternating bit' protocol, B(PN) 2 , Hierarc...