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A theory of timed automata
, 1999
"... Model checking is emerging as a practical tool for automated debugging of complex reactive systems such as embedded controllers and network protocols (see [23] for a survey). Traditional techniques for model checking do not admit an explicit modeling of time, and are thus, unsuitable for analysis of ..."
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Cited by 1964 (31 self)
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Model checking is emerging as a practical tool for automated debugging of complex reactive systems such as embedded controllers and network protocols (see [23] for a survey). Traditional techniques for model checking do not admit an explicit modeling of time, and are thus, unsuitable for analysis of realtime systems whose correctness depends on relative magnitudes of different delays. Consequently, timed automata [7] were introduced as a formal notation to model the behavior of realtime systems. Its definition provides a simple way to annotate statetransition graphs with timing constraints using finitely many realvalued clock variables. Automated analysis of timed automata relies on the construction of a finite quotient of the infinite space of clock valuations. Over the years, the formalism has been extensively studied leading to many results establishing connections to circuits and logic, and much progress has been made in developing verification algorithms, heuristics, and tools. This paper provides a survey of the theory of timed automata, and their role in specification and verification of realtime systems.
An efficient state space generation for the analysis of realtime systems
 ACM Softw. Eng. Notes
, 1996
"... This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of the University of Pennsylvania’s products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this mate ..."
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Cited by 20 (2 self)
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This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of the University of Pennsylvania’s products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to
The Specification and Schedulability Analysis of RealTime Systems using ACSR
 In Proc. of IEEE RealTime Systems Symposium
, 1995
"... To engineer reliable realtime systems, it is desirable to detect timing anomalies early in the development process. However, there is little work addressing the problem of accurately predicting timing properties of realtime systems before implementations are developed. This paper describes an appr ..."
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Cited by 16 (12 self)
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To engineer reliable realtime systems, it is desirable to detect timing anomalies early in the development process. However, there is little work addressing the problem of accurately predicting timing properties of realtime systems before implementations are developed. This paper describes an approach to the specification and schedulability analysis of realtime systems based on the timed process algebra ACSRVP, which is an extension of ACSR with valuepassing communication and dynamic priorities. Combined with the existing features of ACSR for representing time, synchronization and resource requirements, ACSRVP is capable of specifying a variety of realtime systems with different scheduling disciplines in a modular fashion. Moreover, we can perform schedulability analysis on realtime systems specified in ACSRVP automatically by checking for a certain bisimulation relation. 1 Introduction As computers become ubiquitous, they are increasingly used in safety critical environment...
Distributed WebBased Simulation Optimization
, 2000
"... Web technology is having a significant impact on computer simulation. Most of the effort in webbased simulation is aimed at modeling, particularly at building simulation languages and at creating model libraries that can be assembled and executed over the web. We focus on the efficiency of simulati ..."
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Cited by 4 (0 self)
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Web technology is having a significant impact on computer simulation. Most of the effort in webbased simulation is aimed at modeling, particularly at building simulation languages and at creating model libraries that can be assembled and executed over the web. We focus on the efficiency of simulation experimentation for optimization. We introduce a framework for combining the statistical efficiency of simulation optimization techniques with the effectiveness of parallel execution algorithms. In particular, the Optimal Computing Budget Allocation (OCBA) algorithm is implemented in a webbased environment for lowcost parallel and distributed simulation experimentation. A prototype implementation with some experimental results is presented.
CTSM: A Formalism for RealTime System Analysis based on StateSpace Exploration
 Ph.D. Dissertation Proposal
, 1995
"... Traditional approach for analyzing correctness of systems is to identify a set of reachable states and then to analyze this set for verification. This approach is called statespace exploration. Statespace exploration is widely used because it can be easily automated. However verification methods b ..."
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Cited by 2 (2 self)
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Traditional approach for analyzing correctness of systems is to identify a set of reachable states and then to analyze this set for verification. This approach is called statespace exploration. Statespace exploration is widely used because it can be easily automated. However verification methods based on statespace exploration suffer from state explosion, so they are impractical for verifying systems with large state spaces. We propose a method of statespace reduction to cope with the state explosion, especially that caused by large data space and time space. The statespace reduction is crucial because in general, the complexities of existing algorithms for automatic analysis, e.g., modelchecking, depend on the size of the state space. In this proposal, we use Communicating Timed State Machines(CTSM), a state machine based formal model for describing realtime systems. In CTSM, a system consists of concurrent processes communicating with each other through channels. Each process...
A State Minimization Technique for Timed Automata
 In Proc. of Int. Workshop on Veri of In State Systems (INFINITY'96
, 1996
"... The state space of a realtime system can result in an infinite number of states due to unbounded time values. For automatic analysis based on state space exploration, it is important to be able to finitely represent the state space of a realtime system. In this paper, we present an approach that p ..."
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Cited by 1 (0 self)
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The state space of a realtime system can result in an infinite number of states due to unbounded time values. For automatic analysis based on state space exploration, it is important to be able to finitely represent the state space of a realtime system. In this paper, we present an approach that produces a compact representation of the reachable state space of a realtime system. The algorithm yields a small state space, but still retains enough information for analysis. To avoid the state explosion which can be caused by simply adding time values to states, our approach first uses history equivalence and transition bisimulation to collapse states into equivalent classes. To experiment with effectiveness of our approach, we have developed an automatic analysis tool called TREAT. This paper includes the experimental result on Fisher's mutual exclusion protocol. 1 Introduction State explosion is a wellknown problem that impedes analysis and testing based on statespace exploration. ...
An Efficient Generation of the Timed Reachability Graph for the Analysis of RealTime Systems
, 1994
"... As computers become ubiquitous, they are increasingly used in safety critical environments. Since many safety critical applications are realtime systems, automated analysis technique of realtime properties is desirable. Most widely used automated analysis techniques are based on state space exp ..."
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Cited by 1 (0 self)
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As computers become ubiquitous, they are increasingly used in safety critical environments. Since many safety critical applications are realtime systems, automated analysis technique of realtime properties is desirable. Most widely used automated analysis techniques are based on state space exploration. Automatic analysis techniques based on state space exploration suffer from the state space explosion problem. In particular, a realtime system may have an unbounded number of states due to infinitely many possible time values. This paper presents our approach for generating a finite and efficient representation of the reachable states called a timed reachability graph for a realtime system. In this paper, a realtime system is specified using a timed automaton which is a timed extension of the wellknown finite automaton. Our approach for coping with the state explosion problem is to extract timing information from states and to represent it as relative time relations bet...
Hierarchical Reachability State Diagrams  Implementation, Linking and States Composition
 Information System Engineering Research Group, Dept of Electrical and Electronic Engineering, UWA
, 1997
"... : The implementation of Hierarchical Timed Petri Net (HTPN) in our system modelling tool yields a hierarchical analysis method, namely a Hierarchical Reachability State Diagram (HRSD). A Reachability State Diagram (RSD) can be generated for each subnet, and the number of tokens in each HBlock are ..."
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Cited by 1 (1 self)
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: The implementation of Hierarchical Timed Petri Net (HTPN) in our system modelling tool yields a hierarchical analysis method, namely a Hierarchical Reachability State Diagram (HRSD). A Reachability State Diagram (RSD) can be generated for each subnet, and the number of tokens in each HBlock are also record in the state markings. Since the intention of using a HTPN hierarchical representation is to distribute the complexity of a single net over a set of subnets, the HRSD generated for each subnet may also contribute to solving the state explosion problem when representing the system state transitions in a single diagram. An algorithm is outlined to link these HRSDs of the subnets to model the state transitions of the overall system so that the state changes from one HBlock or subnet to another can be linked. Further state search can be performed to locate the sets of states which hold a similar properties to form a group of composition states corresponding to the states in the Sta...
A new method for transforming timed automata
, 2004
"... Discrete events systems (DES) have their behaviors defined by the sequences of events they can execute. For example, communication protocols and computer networks can be seen as DES. Finite state automata (FSA) are convenient for studying (i.e., analyzing, designing) DES, and timed automata (TA) are ..."
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Cited by 1 (0 self)
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Discrete events systems (DES) have their behaviors defined by the sequences of events they can execute. For example, communication protocols and computer networks can be seen as DES. Finite state automata (FSA) are convenient for studying (i.e., analyzing, designing) DES, and timed automata (TA) are convenient for describing realtime DES. An approach for studying a realtime DES, is to transform a TA describing the realtime DES into an equivalent FSA, and then to study the latter. We propose here a new transformation method of TA into FSA. The method is well suited for conformance testing and supervisory control of realtime DES.
WebBased Simulation Experiments
, 1998
"... The use of the World Wide Web and Javabased mobile code provides new opportunities for distributed simulation. First, the infrastructure provided by the Internet eliminates the need for multiprocessor hardware, making it feasible to distribute simulation models over different hardware platforms thr ..."
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The use of the World Wide Web and Javabased mobile code provides new opportunities for distributed simulation. First, the infrastructure provided by the Internet eliminates the need for multiprocessor hardware, making it feasible to distribute simulation models over different hardware platforms through the Internet. Second, "Internetaware" mobile Java code makes the applications fully portable and reusable. These enabling technologies are already exploited for distributed simulation modeling. This paper reports on the preliminary results of an ongoing effort to construct a parallel discrete event simulation support system to distribute simulation experiments over the Internet with a view on simulation optimization. A research prototype for ranking and selection problems is described. The overall project goals are discussed.