Results 1  10
of
96
The algorithmic analysis of hybrid systems
 THEORETICAL COMPUTER SCIENCE
, 1995
"... We present a general framework for the formal specification and algorithmic analysis of hybrid systems. A hybrid system consists of a discrete program with an analog environment. We model hybrid systems as nite automata equipped with variables that evolve continuously with time according to dynamica ..."
Abstract

Cited by 748 (75 self)
 Add to MetaCart
We present a general framework for the formal specification and algorithmic analysis of hybrid systems. A hybrid system consists of a discrete program with an analog environment. We model hybrid systems as nite automata equipped with variables that evolve continuously with time according to dynamical laws. For verification purposes, we restrict ourselves to linear hybrid systems, where all variables follow piecewiselinear trajectories. We provide decidability and undecidability results for classes of linear hybrid systems, and we show that standard programanalysis techniques can be adapted to linear hybrid systems. In particular, we consider symbolic modelchecking and minimization procedures that are based on the reachability analysis of an infinite state space. The procedures iteratively compute state sets that are definable as unions of convex polyhedra in multidimensional real space. We also present approximation techniques for dealing with systems for which the iterative procedures do not converge.
HyTech: A Model Checker for Hybrid Systems
 Software Tools for Technology Transfer
, 1997
"... A hybrid system is a dynamical system whose behavior exhibits both discrete and continuous change. A hybrid automaton is a mathematical model for hybrid systems, which combines, in a single formalism, automaton transitions for capturing discrete change with differential equations for capturing conti ..."
Abstract

Cited by 449 (6 self)
 Add to MetaCart
(Show Context)
A hybrid system is a dynamical system whose behavior exhibits both discrete and continuous change. A hybrid automaton is a mathematical model for hybrid systems, which combines, in a single formalism, automaton transitions for capturing discrete change with differential equations for capturing continuous change. HyTech is a symbolic model checker for linear hybrid automata, a subclass of hybrid automata that can be analyzed automatically by computing with polyhedral state sets. A key feature of HyTech is its ability to perform parametric analysis, i.e. to determine the values of design parameters for which a linear hybrid automaton satisfies a temporallogic requirement. 1 Introduction A hybrid system typically consists of a collection of digital programs that interact with each other and with an analog environment. Examples of hybrid systems include manufacturing controllers, automotive and flight controllers, medical equipment, microelectromechanical systems, and robots. When thes...
A First Step towards Automated Detection of Buffer Overrun Vulnerabilities
 In Network and Distributed System Security Symposium
, 2000
"... We describe a new technique for finding potential buffer overrun vulnerabilities in securitycritical C code. The key to success is to use static analysis: we formulate detection of buffer overruns as an integer range analysis problem. One major advantage of static analysis is that security bugs can ..."
Abstract

Cited by 385 (10 self)
 Add to MetaCart
(Show Context)
We describe a new technique for finding potential buffer overrun vulnerabilities in securitycritical C code. The key to success is to use static analysis: we formulate detection of buffer overruns as an integer range analysis problem. One major advantage of static analysis is that security bugs can be eliminated before code is deployed. We have implemented our design and used our prototype to find new remotelyexploitable vulnerabilities in a large, widely deployed software package. An earlier hand audit missed these bugs. 1.
Verification of RealTime Systems using Linear Relation Analysis
 FORMAL METHODS IN SYSTEM DESIGN
, 1997
"... Linear Relation Analysis [CH78] is an abstract interpretation devoted to the automatic discovery of invariant linear inequalities among numerical variables of a program. In this paper, we apply such an analysis to the verification of quantitative time properties of two kinds of systems: synchronous ..."
Abstract

Cited by 131 (11 self)
 Add to MetaCart
Linear Relation Analysis [CH78] is an abstract interpretation devoted to the automatic discovery of invariant linear inequalities among numerical variables of a program. In this paper, we apply such an analysis to the verification of quantitative time properties of two kinds of systems: synchronous programs and linear hybrid systems.
Hybrid Petri nets
 European Control Conference Grenoble
, 1991
"... Abstract. Petri nets (PNs) are widely used to model discrete event dynamic systems (computer systems, manufacturing systems, communication systems, etc). Continuous Petri nets (in which the markings are real numbers and the transition firings are continuous) were defined more recently; such a PN ma ..."
Abstract

Cited by 125 (0 self)
 Add to MetaCart
Abstract. Petri nets (PNs) are widely used to model discrete event dynamic systems (computer systems, manufacturing systems, communication systems, etc). Continuous Petri nets (in which the markings are real numbers and the transition firings are continuous) were defined more recently; such a PN may model a continuous system or approximate a discrete system. A hybrid Petri net can be obtained if one part is discrete and another part is continuous. This paper is basically a survey of the work of the authors ’ team on hybrid PNs (definition, properties, modeling). In addition, it contains new material such as the definition of extended hybrid PNs and several applications, explanations and comments about the timings in Petri nets, more on the conflict resolution in hybrid PNs, and connection between hybrid PNs and hybrid automata. The paper is illustrated by many examples.
Algorithmic analysis of nonlinear hybrid systems
 in Proc. CAV 95: Computeraided Verification, Lecture Notes in Computer Science
, 1995
"... Abstract—Hybrid systems are digital realtime systems that are embedded in analog environments. Modelchecking tools are available for the automatic analysis of linear hybrid automata, whose environment variables are subject to piecewiseconstant polyhedral differential inclusions. In most embedded ..."
Abstract

Cited by 125 (12 self)
 Add to MetaCart
(Show Context)
Abstract—Hybrid systems are digital realtime systems that are embedded in analog environments. Modelchecking tools are available for the automatic analysis of linear hybrid automata, whose environment variables are subject to piecewiseconstant polyhedral differential inclusions. In most embedded systems, however, the environment variables have differential inclusions that vary with the values of the variables, e.g., _x = x. Such inclusions are prohibited in the linear hybrid automaton model. We present two methods for translating nonlinear hybrid systems into linear hybrid automata. Properties of the nonlinear systems can then be inferred from the automatic analysis of the translated linear hybrid automata. The first method, called clock translation, replaces constraints on nonlinear variables by constraints on clock variables. The clock translation is efficient but has limited applicability. The second method, called linear phaseportrait approximation, conservatively overapproximates the phase portrait of a hybrid automaton using piecewiseconstant polyhedral differential inclusions. Both methods are sound for safety properties; that is, if we establish a safety property of the translated linear system, we may conclude that the original nonlinear system satisfies the property. When applicable, the clock translation is also complete for safety properties; that is, the original system and the translated system satisfy the same safety properties. The phaseportrait approximation method is not complete for safety properties, but it is asymptotically complete; intuitively, for every safety property, and for every relaxed nonlinear system arbitrarily close to the original, if the relaxed system satisfies the safety property, then there is a linear phaseportrait approximation that also satisfies the property. We illustrate both methods by using HYTECH—a symbolic model checker for linear hybrid automata—to automatically check properties of a nonlinear temperature controller and of a predator–prey ecology. Index Terms — Clock translation, formal verification, hybrid systems, HYTECH, linear hybrid automata, model checking, phaseportrait approximation, predator–prey ecologies.
HYTECH: The next generation
 In Proceedings of the 16th IEEE RealTime Systems Symposium
, 1995
"... Abstract. We describe a new implementation of HyTech 1,asymbolic model checker for hybrid systems. Given a parametric description of an embedded system as a collection of communicating automata, HyTech automatically computes the conditions on the parameters under which the system satis es its safety ..."
Abstract

Cited by 120 (9 self)
 Add to MetaCart
(Show Context)
Abstract. We describe a new implementation of HyTech 1,asymbolic model checker for hybrid systems. Given a parametric description of an embedded system as a collection of communicating automata, HyTech automatically computes the conditions on the parameters under which the system satis es its safety and timing requirements. While the original HyTech prototype was based on the symbolic algebra tool Mathematica, the new implementation is written in C ++ and builds on geometric algorithms instead of formula manipulation. The new HyTech o ers a cleaner and more expressive input language, greater portability, superior performance (typically two to three orders of magnitude), and new features such as diagnostic errortrace generation. We illustrate the e ectiveness of the new implementation by applying HyTech to the automatic parametric analysis of the generic railroad crossing benchmark problem [HJL93] and to an active structure control algorithm [ECB94]. 1
Hierarchical Modeling and Analysis of Embedded Systems
, 2003
"... This paper describes the modeling language CHARON for modular design of interacting hybrid systems. The language allows specification of architectural as well as behavioral hierarchy and discrete as well as continuous activities. The modular structure of the language is not merely syntactic, but is ..."
Abstract

Cited by 76 (25 self)
 Add to MetaCart
This paper describes the modeling language CHARON for modular design of interacting hybrid systems. The language allows specification of architectural as well as behavioral hierarchy and discrete as well as continuous activities. The modular structure of the language is not merely syntactic, but is exploited by analysis tools and is supported by a formal semantics with an accompanying compositional theory of refinement. We illustrate the benefits of CHARON in the design of embedded control software using examples from automated highways concerning vehicle coordination
Hybrid Automata with Finite Bisimulations
, 1995
"... . The analysis, verification, and control of hybrid automata with finite bisimulations can be reduced to finitestate problems. We advocate a timeabstract, phasebased methodology for checking if a given hybrid automaton has a finite bisimulation. First, we factor the automaton into two components, ..."
Abstract

Cited by 63 (6 self)
 Add to MetaCart
(Show Context)
. The analysis, verification, and control of hybrid automata with finite bisimulations can be reduced to finitestate problems. We advocate a timeabstract, phasebased methodology for checking if a given hybrid automaton has a finite bisimulation. First, we factor the automaton into two components, a boolean automaton with a discrete dynamics on the finite state space B m and a euclidean automaton with a continuous dynamics on the infinite state space R n . Second, we investigate the phase portrait of the euclidean component. In this fashion, we obtain new decidability results for hybrid systems as well as new, uniform proofs of known decidability results. For example, we prove that if two hybrid automata have finite bisimulations, and both can be calibrated to a common time scale, then their product also has a finite bisimulation. 1 Introduction A hybrid automaton [2] is a mathematical model for a digital program that interacts with an analog environment. Hybrid automata are usef...
Relative Completeness of Abstraction Refinement for Software Model Checking
, 2002
"... Automated methods for an undecidable class of verification problems cannot be complete (terminate for every correct program). We therefore consider a new kind of quality measure for such methods, which is completeness relative to a (powerful but unrealistic) oraclebased method. More precisely, we a ..."
Abstract

Cited by 63 (4 self)
 Add to MetaCart
Automated methods for an undecidable class of verification problems cannot be complete (terminate for every correct program). We therefore consider a new kind of quality measure for such methods, which is completeness relative to a (powerful but unrealistic) oraclebased method. More precisely, we ask whether an often implemented method known as "software model checking with abstraction refinement" is complete relative to fixpoint iteration with "oracleguided" widening. We show that whenever backward fixpoint iteration with oracleguided widening succeeds in proving a property' (for some sequence of widenings determined by the oracle) then software model checking with a particular form of backward refinement will succeed in proving'. Intuitively, this means that the use of fixpoint iteration over abstractions and a particular backwards refinement of the abstractions has the effect of exploring the entire state space of all possible sequences of widenings.