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87
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 64 (27 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.
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 35 (16 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.
Undecidable Problems of Decentralized Observation and Control
, 2001
"... We introduce a new notion of decentralized observability for discreteevent systems, which we call joint observability. We prove that checking joint observability of a regular language w.r.t. one observer is decidable, whereas for two (or more) observers the problem becomes undecidable. Based on thi ..."
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Cited by 35 (3 self)
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We introduce a new notion of decentralized observability for discreteevent systems, which we call joint observability. We prove that checking joint observability of a regular language w.r.t. one observer is decidable, whereas for two (or more) observers the problem becomes undecidable. Based on this result, we show that a related decentralized control problem is also undecidable. We finally provide an extensive study relating our work to existing work in the literature.
Failure Diagnosis of Discrete Event Systems with Lineartime Temporal Logic Fault Specifications
 IEEE Transactions on Automatic Control
, 2001
"... Failure diagnosis problem of discrete event systems with lineartime temporal logic specications is studied in this paper. Diagnosability of discrete event systems in the temporal logic setting is dened. The problem of testing diagnosability is reduced to the problem of model checking. An algorit ..."
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Cited by 33 (4 self)
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Failure diagnosis problem of discrete event systems with lineartime temporal logic specications is studied in this paper. Diagnosability of discrete event systems in the temporal logic setting is dened. The problem of testing diagnosability is reduced to the problem of model checking. An algorithm for the test of diagnosability and the synthesis of a diagnoser is obtained. Finally, a simple example is given for illustration. The contributions of the paper are summarized as follows: (i) For the rst time an algorithm, of complexity polynomial in the number of states of the system and the number of specications, for the diagnoser synthesis is derived in the temporal logic setting; (ii) Usage of temporal logic makes the specication specifying process easier and userfriendly since natural language specications can be easily translated to temporal logic specications (when compared to formal language/automatabased specications), yet there are computational savings in the design of diagnoser (compared to that of formal language/automatabased specications); (iii) LTLbased failure diagnosis method can capture the failures representing violation of liveness properties which can not be captured by prior formal language/automatonbased failure diagnosis methods, which can only capture failures representing violation of safety properties (such as occurrence of a faulty event, or reaching a faulty state, etc.); (iv) By reducing the problem of testing diagnosability to that of model checking (and using the model checking to test the diagnosability) , a polynomial algorithm for testing diagnosability is obtained naturally; whence by using symbolic model checking we may test the diagnosability of large systems more eciently; (v) We relaxed the requirement...
A protocol for multiagent diagnosis with spatially distributed knowledge
 In AAMAS 2003
, 2003
"... In a large distributed system it is often infeasible or even impossible to maintain a model of the whole system. Instead, several spatially distributed local models of the system have to be used to detect possible faults. Traditional diagnostic tools cannot handle such a set of spatially distributed ..."
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Cited by 32 (6 self)
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In a large distributed system it is often infeasible or even impossible to maintain a model of the whole system. Instead, several spatially distributed local models of the system have to be used to detect possible faults. Traditional diagnostic tools cannot handle such a set of spatially distributed local models. A MultiAgent System of diagnostic agents, where each agent has a model 1 of a subsystem, may offer solutions for establishing a global diagnosis of a large distributed system. Unfortunately, any protocol that establishes a global minimal diagnosis, is NPHard, even if an agent can determine local minimal diagnoses in polynomial time. This paper presents a protocol that enables agents to determine local minimal diagnoses that are consistent with global diagnoses. Moreover, the protocol ensures that no agent acquires knowledge of global diagnoses. The protocol does not guarantee that a combination of the agents ’ local minimal diagnoses is also a global minimal diagnosis. However, for every global minimal diagnosis, there is a combination of local minimal diagnosis. 1
Diagnosis of Asynchronous Discrete Event Systems: Datalog to the Rescue!
 IN ACM PODS
, 2005
"... We consider query optimization techniques for data intensive P2P applications. We show how to adapt an old technique from deductive databases, namely QuerySubQuery (QSQ), to a setting where autonomous and distributed peers share large volumes of interelated data. We illustrate the technique with a ..."
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Cited by 31 (12 self)
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We consider query optimization techniques for data intensive P2P applications. We show how to adapt an old technique from deductive databases, namely QuerySubQuery (QSQ), to a setting where autonomous and distributed peers share large volumes of interelated data. We illustrate the technique with an important telecommunication problem, the diagnosis of distributed telecom systems. We show that (i) the problem can be modeled using Datalog programs, and (ii) it can benefit from the large battery of optimization techniques developed for Datalog. In particular, we show that a simple generic use of the extension of QSQ achieves an optimization as good as that previously provided by dedicated diagnosis algorithms. Furthermore, we show that it allows solving efficiently a much larger class of system analysis problems.
Markov Nets: Probabilistic Models for distributed and concurrent systems
 IEEE Transactions on Automatic Control
, 2001
"... For distributed systems, i.e. large networked complex systems, there is a drastic difference between a local view and knowledge of the system, and its global view. Distributed systems have local state and time, but do not possess global state and time in the usual sense. In this paper, motivated by ..."
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Cited by 30 (15 self)
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For distributed systems, i.e. large networked complex systems, there is a drastic difference between a local view and knowledge of the system, and its global view. Distributed systems have local state and time, but do not possess global state and time in the usual sense. In this paper, motivated by the monitoring of distributed systems and in particular of telecommunications networks, we develop Markov nets as an extension of Markov chains and hidden Markov models (Hmm) for distributed and concurrent systems. By a concurrent system, we mean a system in which components may evolve independently, with sparse synchronizations. We follow a socalled true concurrency approach, in which neither global state nor global linear time are available. Instead, we use only local states in combination with a partial order model of time. Our basic mathematical tool is that of Petri net unfoldings. Keywords : discrete event systems, stochastic Petri nets, unfoldings. 1 Motivations Distributed network...
A decentralized modelbased diagnostic tool for complex systems
 In International Journal on Artificial Intelligence Tools. World Scientific Publishing Company
"... We address the problem of diagnosing complex discreteevent systems such as telecommunication networks1. Given a flow of observations from the system, the goal is to explain those observations by identifying and localizing possible faults. Several modelbased diagnosis approaches deal with this probl ..."
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Cited by 28 (6 self)
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We address the problem of diagnosing complex discreteevent systems such as telecommunication networks1. Given a flow of observations from the system, the goal is to explain those observations by identifying and localizing possible faults. Several modelbased diagnosis approaches deal with this problem but they need the computation of a global model which is not feasible for complex systems like telecommunication networks. Our contribution is the proposal of a decentralized approach which permits to carry out an online diagnosis without computing the global model. This paper describes the implementation of a tool based on this approach. Given a decentralized model of the system and a flow of observations, the program analyzes the flow and computes the diagnosis in a decentralized way. We also present experimental results based on a real system. 1.
Decentralized diagnoser approach: application to telecommunication networks
 In Proc. of the International Workshop on Principles of Diagnosis (DX’00
, 2000
"... This paper presents a general method for the diagnosis of large systems, such as telecommunication networks. Because of the size of the system, the model we use is decentralized. In order to increase the efficiency of the diagnosis, the method combines two basic techniques of diagnosis: diagnosers a ..."
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Cited by 28 (4 self)
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This paper presents a general method for the diagnosis of large systems, such as telecommunication networks. Because of the size of the system, the model we use is decentralized. In order to increase the efficiency of the diagnosis, the method combines two basic techniques of diagnosis: diagnosers and simulationbased techniques. We propose the construction of diagnosers based on local behaviors to compute local diagnoses. Then, we propose a coordination of local diagnoses based on a strategy which minimizes the computation for the coordination.
Minimal Communication in a Distributed DiscreteEvent System
, 2000
"... Distributed discreteevent systems, in which agents (or local sites) are required to communicate in order to perform some speci ed monitoring and control tasks, are considered. Each agentis modeled as a nitestate machine that must be able to distinguish between its states to perform some required t ..."
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Cited by 27 (9 self)
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Distributed discreteevent systems, in which agents (or local sites) are required to communicate in order to perform some speci ed monitoring and control tasks, are considered. Each agentis modeled as a nitestate machine that must be able to distinguish between its states to perform some required task. To help it disambiguate states, an agent uses a combination of direct observation (obtained from sensor readings available to that agent) and communicated information (obtained from sensor readings available to another agent). Since communication may be costly, a strategy to minimize communication between sites is developed. The complexity of the solution re ects the interdependence of the agents' communication protocols. That is, the decision to communicate the occurrence of an event relies on which event sequences are indistinguishable to an agent, which, in turn, is a result of what has already been communicated to that agent.