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41
Binary Reachability Analysis of Discrete Pushdown Timed Automata
 CAV'00, LNCS 1855
, 2000
"... . We introduce discrete pushdown timed automata that are timed automata with integervalued clocks augmented with a pushdown stack. A configuration of a discrete pushdown timed automaton includes a control state, finitely many clock values and a stack word. Using a pure automatatheoretic approa ..."
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Cited by 45 (28 self)
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. We introduce discrete pushdown timed automata that are timed automata with integervalued clocks augmented with a pushdown stack. A configuration of a discrete pushdown timed automaton includes a control state, finitely many clock values and a stack word. Using a pure automatatheoretic approach, we show that the binary reachability (i.e., the set of all pairs of configurations (ff; fi), encoded as strings, such that ff can reach fi through 0 or more transitions) can be accepted by a nondeterministic pushdown machine augmented with reversalbounded counters (NPCM). Since discrete timed automata with integervalued clocks can be treated as discrete pushdown timed automata without the pushdown stack, we can show that the binary reachability of a discrete timed automaton can be accepted by a nondeterministic reversalbounded multicounter machine. Thus, the binary reachability is Presburger. By using the known fact that the emptiness problem is decidable for reversalbounded ...
Objectoriented Modeling with ADORA
, 2002
"... In this paper, we present the Adora approac to objectoriented modeling of software (Adora stands for analysis and description of requirements and arc itecture). T e main features of Adora t at distinguis it from ot er approac es like UML are t e use of abstract objects (instead of classes) as t e b ..."
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Cited by 28 (14 self)
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In this paper, we present the Adora approac to objectoriented modeling of software (Adora stands for analysis and description of requirements and arc itecture). T e main features of Adora t at distinguis it from ot er approac es like UML are t e use of abstract objects (instead of classes) as t e basis of t e model, a systematic hierarchical decomposition of t e modeled system and t e integration of all aspects of t e system in one coherent model. T e paper introduces t e concepts of Adora and t e rationale be ind t em, gives an overview of t e language, sketc es a novel concept for visualizing t e model ierarc y wit a tool and reports t e results of a validation experiment for t e Adora language. r 2002 ElsevierSsevie Ltd. All rig ts reserved.
Pushdown Timed Automata: a Binary Reachability Characterization and Safety Verification
 Theoretical Computer Science
, 2003
"... We consider pushdown timed automata (PTAs) that are timed automata (with dense clocks) augmented with a pushdown stack. A configuration of a PTA includes a state, dense clock values and a stack word. By using the pattern technique, we give a decidable characterization of the binary reachability ( ..."
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Cited by 21 (8 self)
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We consider pushdown timed automata (PTAs) that are timed automata (with dense clocks) augmented with a pushdown stack. A configuration of a PTA includes a state, dense clock values and a stack word. By using the pattern technique, we give a decidable characterization of the binary reachability (i.e., the set of all pairs of configurations such that one can reach the other) of a PTA. Since a timed automaton can be treated as a PTA without the pushdown stack, we can show that the binary reachability of a timed automaton is definable in the additive theory of reals and integers. The results can be used to verify a class of properties containing linear relations over both dense variables and unbounded discrete variables. The properties previously could not be verified using the classic region technique nor expressed by timed temporal logics for timed automata and CTL for pushdown systems. The results are also extended to other generalizations of timed automata.
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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Binary Reachability Analysis of Pushdown Timed Automata with Dense Clocks
 In CAV’01, volume 2102 of LNCS
"... . We consider pushdown timed automata (PTAs) that are timed automata (with dense clocks) augmented with a pushdown stack. A configuration of a PTA includes a control state, dense clock values and a stack word. By using the pattern technique, we give a decidable characterization of the binary reachab ..."
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Cited by 15 (10 self)
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. We consider pushdown timed automata (PTAs) that are timed automata (with dense clocks) augmented with a pushdown stack. A configuration of a PTA includes a control state, dense clock values and a stack word. By using the pattern technique, we give a decidable characterization of the binary reachability (i.e., the set of all pairs of configurations such that one can reach the other) of a PTA. Since a timed automaton can be treated as a PTA without the pushdown stack, we can show that the binary reachability of a timed automaton is definable in the additive theory of reals and integers. The results can be used to verify a class of properties containing linear relations over both dense variables and unbounded discrete variables. The properties previously could not be verified using the classic region technique nor expressed by timed temporal logics for timed automata and CTL for pushdown systems. 1 Introduction A timed automaton [3] can be considered as a finite automaton augmented...
The Design and Analysis of RealTime Systems Using the ASTRAL Software Development Environment
 ANNALS OF SOFTWARE ENGINEERING
, 1999
"... ASTRAL is a formal specification language for realtime systems. It is intended to support formal software development and, therefore, has been formally defined. The structuring mechanisms in ASTRAL allow one to build modularized specifications of complex systems with layering. A realtime system is ..."
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Cited by 14 (14 self)
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ASTRAL is a formal specification language for realtime systems. It is intended to support formal software development and, therefore, has been formally defined. The structuring mechanisms in ASTRAL allow one to build modularized specifications of complex systems with layering. A realtime system is modeled by a collection of state machine specifications and a single global specification. This paper discusses the ASTRAL Software Development Environment (SDE), which is an integrated set of design and analysis tools based on the ASTRAL formal framework. The tools that make up the support environment are a syntaxdirected editor, a specification processor, a verification condition generator, a browser kit, a model checker, and a mechanical theorem prover.
On Presburger Liveness of Discrete Timed Automata
 STACS'01, LNCS 2010
, 2001
"... Using an automatatheoretic approach, we investigate the decidabilityof liveness properties (called Presburger liveness properties) for timed automata when Presburger formulas on configurations are allowed. While the general problem of checking a temporal logic such as TPTL augmented with Presburg ..."
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Cited by 13 (12 self)
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Using an automatatheoretic approach, we investigate the decidabilityof liveness properties (called Presburger liveness properties) for timed automata when Presburger formulas on configurations are allowed. While the general problem of checking a temporal logic such as TPTL augmented with Presburger clock constraints is undecidable, we show that there are various classes of Presburgerliveness properties which are decidable for discrete timed automata. For instance, it is decidable, given a discrete timed automaton A and a Presburger property P,whether there exists an!path of A where P holds infinitely often. We also showthat other classes of Presburger liveness properties are indeed undecidable for discrete timed automata, e.g., whether P holds infinitely often for each!path of A. These results might give insights into the corresponding problems for timedautomata over dense domains, and help in the definition of a fragment of linear temporal logic, augmented with Presburger conditions on configurations, whichis decidable for model checking timed automata.
Network Topology and a Case Study in TCOZ
 The 11th International Conference of Z Users, volume 1493 of Lecture Notes in Computer Science
, 1998
"... ObjectZ is strong in modeling the data and operations of complex systems. However, it is weak in specifying realtime and concurrent systems. The Timed Communicating ObjectZ (TCOZ) extends ObjectZ notation with Timed CSP's constructs. TCOZ is particularly well suited for specifying complex s ..."
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Cited by 9 (5 self)
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ObjectZ is strong in modeling the data and operations of complex systems. However, it is weak in specifying realtime and concurrent systems. The Timed Communicating ObjectZ (TCOZ) extends ObjectZ notation with Timed CSP's constructs. TCOZ is particularly well suited for specifying complex systems whose components have their own thread of control. This paper demonstrates expressiveness of the TCOZ notation through a case study on specifying a multilift system that operates in realtime.
Presburger Liveness Verification of Discrete Timed Automata
, 2003
"... Using an automatatheoretic approach, we investigate the decidability of liveness properties (called Presburger liveness properties) for timed automata when Presburger formulas on configurations are allowed. While the general problem of checking a temporal logic such as TPTL augmented with Presburge ..."
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Cited by 8 (4 self)
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Using an automatatheoretic approach, we investigate the decidability of liveness properties (called Presburger liveness properties) for timed automata when Presburger formulas on configurations are allowed. While the general problem of checking a temporal logic such as TPTL augmented with Presburger clock constraints is undecidable, we show that there are various classes of Presburger liveness properties which are decidable for discrete timed automata. For instance, it is decidable, given a discrete timed automaton A and a Presburger property P , whether there exists an !path of A where P holds infinitely often. We also show that other classes of Presburger liveness properties are indeed undecidable for discrete timed automata, e.g., whether P holds infinitely often for each !path of A . These results might give insights into the corresponding problems for timed automata over dense domains, and help in the definition of a fragment of linear temporal logic, augmented with Presburger conditions on configurations, which is decidable for model checking timed automata.
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