TY - CONF
AB - We define robust timed automata, which are timed automata that accept all trajectories robustly: if a robust timed automaton accepts a trajectory, then it must accept neighboring trajectories also; and if a robust timed automaton rejects a trajectory, then it must reject neighboring trajectories also. We show that the emptiness problem for robust timed automata is still decidable, by modifying the region construction for timed automata. We then show that, like timed automata, robust timed automata cannot be determinized. This result is somewhat unexpected, given that in temporal logic, the removal of realtime equality constraints is known to lead to a decidable theory that is closed under all boolean operations.
AU - Gupta, Vineet
AU - Thomas Henzinger
AU - Jagadeesan, Radha
ID - 4520
TI - Robust timed automata
VL - 1201
ER -
TY - CONF
AB - In a trace-based world, the modular specification, verification, and control of live systems require each module to be receptive; that is, each module must be able to meet its liveness assumptions no matter how the other modules behave. In a real-time world, liveness is automatically present in the form of diverging time. The receptiveness condition, then, translates to the requirement that a module must be able to let time diverge no matter how the environment behaves. We study the receptiveness condition for real-time systems by extending the model of reactive modules to timed and hybrid modules. We define the receptiveness of such a module as the existence of a winning strategy in a game of the module against its environment. By solving the game on region graphs, we present an (optimal) Exptime algorithm for checking the receptiveness of prepositional timed modules. By giving a fixpoint characterization of the game, we present a symbolic procedure for checking the receptiveness of linear hybrid modules. Finally, we present an assume-guarantee principle for reasoning about timed and hybrid modules, and a method for synthesizing receptive controllers of timed and hybrid modules.
AU - Alur, Rajeev
AU - Thomas Henzinger
ID - 4583
TI - Modularity for timed and hybrid systems
VL - 1243
ER -
TY - JOUR
AB - This paper introduces, gently but rigorously, the clock approach to real-time programming. We present with mathematical precision, assuming no prerequisites other than familiarity with logical and programming notations, the concepts that are necessary for understanding, writing, and executing clock programs. In keeping with an expository style, all references are clustered in bibliographic remarks at the end of each section. The first appendix presents proof rules for verifying temporal properties of clock programs. The second appendix points to selected literature on formal methods and tools for programming with clocks. In particular, the timed automaton, which is a finite-state machine equipped with clocks, has become a standard paradigm for real-time model checking; it underlies the tools HyTech, Kronos, and Uppaal, which are discussed elsewhere in this volume.
AU - Alur, Rajeev
AU - Thomas Henzinger
ID - 4584
IS - 1-2
JF - Software Tools For Technology Transfer
TI - Real-time system = discrete system + clock variables
VL - 1
ER -
TY - CONF
AB - 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. In this survey, we demonstrate symbolic algorithms for the verification of and controller synthesis for linear hybrid automata, a subclass of hybrid automata that can be analyzed automatically
AU - Alur, Rajeev
AU - Thomas Henzinger
AU - Wong-Toi, Howard
ID - 4605
TI - Symbolic analysis of hybrid systems
ER -
TY - JOUR
AB - We present a verification algorithm for duration properties of real-time systems. While simple real-time properties constrain the total elapsed time between events, duration properties constrain the accumulated satisfaction time of state predicates. We formalize the concept of durations by introducing duration measures for timed automata. A duration measure assigns to each finite run of a timed automaton a real number —the duration of the run— which may be the accumulated satisfaction time of a state predicate along the run. Given a timed automaton with a duration measure, an initial and a final state, and an arithmetic constraint, the duration-bounded reachability problem asks if there is a run of the automaton from the initial state to the final state such that the duration of the run satisfies the constraint. Our main result is an (optimal) PSPACE decision procedure for the duration-bounded reachability problem.
AU - Alur, Rajeev
AU - Courcoubetis, Costas
AU - Thomas Henzinger
ID - 4607
IS - 2
JF - Formal Methods in System Design
TI - Computing accumulated delays in real-time systems
VL - 11
ER -