Results 1  10
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141
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 2651 (32 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.
What's Decidable about Hybrid Automata?
 Journal of Computer and System Sciences
, 1995
"... . Hybrid automata model systems with both digital and analog components, such as embedded control programs. Many verification tasks for such programs can be expressed as reachability problems for hybrid automata. By improving on previous decidability and undecidability results, we identify a boundar ..."
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Cited by 377 (16 self)
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. Hybrid automata model systems with both digital and analog components, such as embedded control programs. Many verification tasks for such programs can be expressed as reachability problems for hybrid automata. By improving on previous decidability and undecidability results, we identify a boundary between decidability and undecidability for the reachability problem of hybrid automata. On the positive side, we give an (optimal) PSPACE reachability algorithm for the case of initialized rectangular automata, where all analog variables follow independent trajectories within piecewiselinear envelopes and are reinitialized whenever the envelope changes. Our algorithm is based on the construction of a timed automaton that contains all reachability information about a given initialized rectangular automaton. The translation has practical significance for verification, because it guarantees the termination of symbolic procedures for the reachability analysis of initialized rectangular autom...
Blackbox conformance testing for realtime systems
 In 11th International SPIN Workshop on Model Checking of Software (SPIN’04), volume 2989 of LNCS
, 2004
"... We propose a new framework for blackbox conformance testing of realtime systems. The framework is based on the model of partiallyobservable, nondeterministic timed automata. We argue that partial observability and nondeterminism are essential features for ease of modeling, expressiveness and im ..."
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Cited by 76 (11 self)
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We propose a new framework for blackbox conformance testing of realtime systems. The framework is based on the model of partiallyobservable, nondeterministic timed automata. We argue that partial observability and nondeterminism are essential features for ease of modeling, expressiveness and implementability. The framework allows the user to define, through appropriate modeling, assumptions on the environment of the system under test (SUT) as well as on the interface between the tester and the SUT. We consider two types of tests: analogclock tests and digitalclock tests. Our algorithm to generate analogclock tests is based on an onthefly determinization of the specification automaton during the execution of the test, which in turn relies on reachability computations. The latter can sometimes be costly, thus problematic, since the tester must quickly react to the actions of the system under test. Therefore, we provide techniques which allow analogclock testers to be represented as deterministic timed automata, thus minimizing the reaction time to a simple state jump. We provide algorithms for static or onthefly generation of digitalclock tests. These tests measure time only with finiteprecision, digital clocks, another essential condition for implementability. We also propose a technique for location, edge and state coverage of the specification, by reducing the problem to covering a symbolic reachability graph. This avoids having to generate too many tests. We report on a prototype tool TTG and two case studies: a lighting device and the Bounded Retransmission Protocol. Experimental results obtained by applying TTG on the Bounded Retransmission Protocol show that only a few tests suffice to cover thousands of reachable symbolic states in the specification.
Performance analysis of probabilistic timed automata using digital clocks
 Proc. Formal Modeling and Analysis of Timed Systems (FORMATS’03), volume 2791 of LNCS
, 2003
"... ..."
Online Testing of Realtime Systems using UPPAAL
 INTERNATIONAL WORKSHOP ON FORMAL APPROACHES TO TESTING OF SOFTWARE. COLOCATED WITH IEEE CONFERENCE ON AUTOMATES SOFTWARE ENGINEERING 2004
, 2004
"... This chapter presents principles and techniques for modelbased blackbox conformance testing of realtime systems using the Uppaal modelchecking toolsuite. The basis for testing is given as a network of concurrent timed automata specified by the test engineer. Relativized input/output conformance ..."
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Cited by 73 (11 self)
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This chapter presents principles and techniques for modelbased blackbox conformance testing of realtime systems using the Uppaal modelchecking toolsuite. The basis for testing is given as a network of concurrent timed automata specified by the test engineer. Relativized input/output conformance serves as the notion of implementation correctness, essentially timed trace inclusion taking environment assumptions into account. Test cases can be generated offline and later executed, or they can be generated and executed online. For both approaches this chapter discusses how to specify test objectives, derive test sequences, apply these to the system under test, and assign a verdict.
Integration Graphs: A Class of Decidable Hybrid Systems
 In Hybrid Systems, volume 736 of Lecture Notes in Computer Science
, 1993
"... . Integration Graphs are a computational model developed in the attempt to identify simple Hybrid Systems with decidable analysis problems. We start with the class of constant slope hybrid systems (cshs), in which the right hand side of all differential equations is an integer constant. We refer to ..."
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Cited by 72 (10 self)
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. Integration Graphs are a computational model developed in the attempt to identify simple Hybrid Systems with decidable analysis problems. We start with the class of constant slope hybrid systems (cshs), in which the right hand side of all differential equations is an integer constant. We refer to continuous variables whose right hand side constants are always 1 as timers. All other continuous variables are called integrators. The first result shown in the paper is that simple questions such as reachability of a given state are undecidable for even this simple class of systems. To restrict the model even further, we impose the requirement that no test that refers to integrators may appear within a loop in the graph. This restricted class of cshs is called integration graphs . The main results of the paper are that the reachability problem of integration graphs is decidable for two special cases: The case of a single timer and the case of a single test involving integrators. The expres...
On the decidability of metric temporal logic
 In Proc. LICS
, 2005
"... Metric Temporal Logic (MTL) is a prominent specification formalism for realtime systems. In this paper, we show that the satisfiability problem for MTL over finite timed words is decidable, with nonprimitive recursive complexity. We also consider the modelchecking problem for MTL: whether all w ..."
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Cited by 68 (10 self)
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Metric Temporal Logic (MTL) is a prominent specification formalism for realtime systems. In this paper, we show that the satisfiability problem for MTL over finite timed words is decidable, with nonprimitive recursive complexity. We also consider the modelchecking problem for MTL: whether all words accepted by a given AlurDill timed automaton satisfy a given MTL formula. We show that this problem is decidable over finite words. Over infinite words, we show that model checking the safety fragment of MTL—which includes invariance and timebounded response properties—is also decidable. These results are quite surprising in that they contradict various claims to the contrary that have appeared in the literature. The question of the decidability of MTL over infinite words remains open. 1.
Some progress in the symbolic verification of timed automata
 IN PROC. OF THE 8TH CONFERENCE ON COMPUTERAIDED VERI CATION
, 1997
"... In this paper we discuss the practical difficulty of analyzing the behavior of timed automata and report some results obtained using an experimental bddbased extension of kronos. We have treated examples originating from timing analysis of asynchronous boolean networks and CMOS circuits with delay ..."
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Cited by 53 (4 self)
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In this paper we discuss the practical difficulty of analyzing the behavior of timed automata and report some results obtained using an experimental bddbased extension of kronos. We have treated examples originating from timing analysis of asynchronous boolean networks and CMOS circuits with delay uncertainties and the results outperform those obtained by previous implementations of timed automata verification tools.
Temporal Proof Methodologies for Timed Transition Systems
 INFORMATION AND COMPUTATION
, 1994
"... We extend the specification language of temporal logic, the corresponding verification framework, and the underlying computational model to deal with realtime properties of reactive systems. The abstract notion of timed transition systems generalizes traditional transition systems conservatively: ..."
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Cited by 50 (8 self)
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We extend the specification language of temporal logic, the corresponding verification framework, and the underlying computational model to deal with realtime properties of reactive systems. The abstract notion of timed transition systems generalizes traditional transition systems conservatively: qualitative fairness requirements are replaced (and superseded) by quantitative lowerbound and upperbound timing constraints on transitions. This framework can model realtime systems that communicate either through shared variables or by message passing and realtime issues such as timeouts, process priorities (interrupts), and process scheduling. We exhibit two styles for the specification of realtime systems. While the first approach uses timebounded versions of the temporal operators, the second approach allows explicit references to time through a special clock variable. Corresponding to the two styles of specification, we present and compare two different proof methodologies for t...