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14
Using the ASTRAL model checker to analyze mobile IP,”
 in ICSE ’99: Proceedings of the 21st international conference on Software engineering.
, 1999
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Tools and Techniques for the Design and Systematic Analysis of RealTime Systems
, 1999
"... As technology progresses and computers become smaller, cheaper, and more powerful, they are increasingly relied on to guarantee the safety of human life and the environment. In most cases, it is not enough to merely provide such safety mechanisms, but is also critical to assure that they will be a ..."
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Cited by 8 (4 self)
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As technology progresses and computers become smaller, cheaper, and more powerful, they are increasingly relied on to guarantee the safety of human life and the environment. In most cases, it is not enough to merely provide such safety mechanisms, but is also critical to assure that they will be activated in time to prevent disasters. These realtime systems are found in both largescale projects with highly visible consequences such as nuclear reactors and air traffic control systems as well as in consumer goods such as automobiles and smoke detectors. As more and more reliance is placed on realtime computing systems to perform critical and everyday functions, the need for formal methods to guarantee the correctness of these systems becomes crucial. Given the time
Past Pushdown Timed Automata and Safety Verification
 Theoretical Computer Science
"... We consider past pushdown timed automata that are discrete pushdown timed automata with past formulas as enabling conditions. Using past formulas allows a past pushdown timed automaton to access the past values of the finite state variables in the automaton. We prove that the reachability (i.e., the ..."
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Cited by 6 (0 self)
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We consider past pushdown timed automata that are discrete pushdown timed automata with past formulas as enabling conditions. Using past formulas allows a past pushdown timed automaton to access the past values of the finite state variables in the automaton. We prove that the reachability (i.e., the set of reachable configurations from an initial configuration) of a past pushdown timed automaton can be accepted by a nondeterministic reversalbounded counter machine augmented with a pushdown stack (i.e., a reversalbounded NPCM). By using the known fact that the emptiness problem for reversalbounded NPCMs is decidable, we show that modelchecking past pushdown timed automata against Presburger safety properties on discrete clocks and stack word counts is decidable. We also investigate the reachability problem for a class of transition systems under some fairness constraints in the form of generalized past formulas. Finally, we present an example ASTRAL specification to demonstrate the usefulness of the results.
A Symbolic Model Checker for Testing ASTRAL Realtime Specifications
 PROC. OF RTCSA'99
, 1999
"... ASTRAL is a highlevel formal specification language for realtime (infinite state) systems. It is provided with structuring mechanisms that allow one to build modularized specifications of complex realtime systems with layering. In this paper, the methods and techniques used in the prototype imple ..."
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Cited by 6 (6 self)
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ASTRAL is a highlevel formal specification language for realtime (infinite state) systems. It is provided with structuring mechanisms that allow one to build modularized specifications of complex realtime systems with layering. In this paper, the methods and techniques used in the prototype implementation of the ASTRAL symbolic model checker, which is a component of the ASTRAL Software Development Environment(SDE), are presented. The model checking procedure uses the Omega library to represent a subset of states, and model checking is carried out on the execution tree of an ASTRAL process. The tree is further trimmed by the execution graph of the process. The model checker combines both explicit state exploration and symbolic state calculation in order to reduce the number of variables needed by dynamically resolving their values as well as their histories along a path of execution. Based upon the ASTRAL proof theory, the model checker is modularized, in the sense that each time it ...
Generalized discrete timed automata: decidable approximations for safety verification
 Theoretical Computer Science
"... Abstract. We consider generalized discrete timed automata with general linearrelations over clocks and parameterized constants as clock constraints and with parameterized durations. We look at three approximation techniques (i.e., the rresetbounded approximation, the Bbounded approximation, and t ..."
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Cited by 4 (4 self)
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Abstract. We consider generalized discrete timed automata with general linearrelations over clocks and parameterized constants as clock constraints and with parameterized durations. We look at three approximation techniques (i.e., the rresetbounded approximation, the Bbounded approximation, and the hB; ricrossingbounded approximation), and derive automatatheoretic characterizations of the binary reachability under these approximations. The characterizations allow us to show that the safety analysis problem is decidable for generalized discrete timed automata with unit durations and for deterministic generalizeddiscrete timed automata with parameterized durations. An example specification written in ASTRAL is used to run a number of experiments using one of theapproximation techniques. 1 Introduction As a standard model for analyzing realtime systems, timed automata [3] have receivedenormous attention during the past decade. A timed automaton can be considered as a finite automaton augmented with a finite number of clocks. The clocks can be reset orprogress at the same rate, and can be tested against clock constraints in the form of clock regions (i.e., comparisons of a clock or the difference of two clocks against an integerconstant, e.g.,
Three Approximation Techniques for ASTRAL Symbolic Model Checking of Infinite State Realtime Systems
 IN PROCEEDINGS OF THE 22ND INTERNATIONAL CONFERENCE ON SOFTWARE ENGINEERING
, 2000
"... ASTRAL is a highlevel formal specification language for realtime systems. It has structuring mechanisms that allow one to build modularized specifications of complex realtime systems with layering. Based upon the ASTRAL symbolic model checker reported in [13], three approximation techniques to sp ..."
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Cited by 4 (3 self)
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ASTRAL is a highlevel formal specification language for realtime systems. It has structuring mechanisms that allow one to build modularized specifications of complex realtime systems with layering. Based upon the ASTRAL symbolic model checker reported in [13], three approximation techniques to speedup the model checking process for use in debugging a specification are presented. The techniques are random walk, partial image and dynamic environment generation. Ten mutation tests on a railroad crossing benchmark are used to compare the performance of the techniques applied separately and in combination. The test results are presented and analyzed.
Proof Assistance for RealTime Systems Using an Interactive Theorem Prover
 5th International AMAST Workshop on RealTime and Probabilistic Systems, LNCS
"... . This paper discusses the adaptation of the PVS theorem prover for performing analysis of realtime systems written in the ASTRAL formal specification language. A number of issues were encountered during the encoding of ASTRAL that are relevant to the encoding of many realtime specification la ..."
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Cited by 3 (0 self)
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. This paper discusses the adaptation of the PVS theorem prover for performing analysis of realtime systems written in the ASTRAL formal specification language. A number of issues were encountered during the encoding of ASTRAL that are relevant to the encoding of many realtime specification languages. These issues are presented as well as how they were handled in the ASTRAL encoding. A translator has been written that translates any ASTRAL specification into its corresponding PVS encoding. After performing the proofs of several systems using the encoding, PVS strategies have been developed to automate the proofs of certain types of properties. In addition, the encoding has been used as the basis for a transition sequence generator tool. 1 Introduction A realtime system is a system that must perform its actions within specified time bounds. With the advent of cheap processing power and increasingly sophisticated consumer demands, realtime systems have become commonplace ...
Decidable Approximations on Generalized and Parameterized Discrete Timed Automata
 COCOON'01, LNCS 2108
"... . We consider generalized discrete timed automata with general linear relations over clocks and parameterized constants as clock constraints and with parameterized durations. We look at three approximation techniques (i.e., the rresetbounded approximation, the Bbounded approximation, and the hB ..."
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Cited by 2 (2 self)
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. We consider generalized discrete timed automata with general linear relations over clocks and parameterized constants as clock constraints and with parameterized durations. We look at three approximation techniques (i.e., the rresetbounded approximation, the Bbounded approximation, and the hB; ricrossingbounded approximation), and derive automatatheoretic characterizations of the binary reachability under these approximations. The characterizations allow us to show that the safety analysis problem is decidable for generalized discrete timed automata with unit durations and for deterministic generalized discrete timed automata with parameterized durations. An example specification written in ASTRAL is used to run a number of experiments using one of the approximation techniques. 1
Dynamic Environment Generations for an ASTRAL Process
"... ASTRAL is a highlevel formal specification language for realtime systems. It includes structuring mechanisms that allow one to build modularized specifications of complex realtime systems with layering. Based upon the ASTRAL symbolic model checker reported in [DK99b], an approximation techniq ..."
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Cited by 1 (1 self)
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ASTRAL is a highlevel formal specification language for realtime systems. It includes structuring mechanisms that allow one to build modularized specifications of complex realtime systems with layering. Based upon the ASTRAL symbolic model checker reported in [DK99b], an approximation technique to speedup the ASTRAL symbolic model checker for debugging a specification is presented. The technique, called dynamic environment generation, randomly generates a sequence of concrete environments for an ASTRAL process instance along each execution path in the execution tree of the ASTRAL process. Doing this greatly reduces the time for finding an error in a specification, as demonstrated by a number of mutation tests, while still ensuring reasonable coverage of the search procedure. The results of the tests show that the techniques presented in the paper are effective.
Past Pushdown Timed Automata (Extended Abstract)
"... Region reachability is useful, but obviously not enough. For instance, we may wantto know whether clock values satisfying a nonregion property ..."
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Region reachability is useful, but obviously not enough. For instance, we may wantto know whether clock values satisfying a nonregion property