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In this paper, we introduce a parametric semantics for timed controllers called the Almost ASAP semantics. This semantics is a relaxation of the usual ASAP semantics (also called the maximal progress semantics) which is a mathematical idealization that can not be implemented by any physical device no matter how fast it is. On the contrary, any correct… (More)

We propose and evaluate a new algorithm for checking the universality of nondeterministic finite automata. In contrast to the standard algorithm, which uses the subset construction to explicitly deter-minize the automaton, we keep the determinization step implicit. Our algorithm computes the least fixed point of a monotone function on the lattice of… (More)

In this paper, we propose a fixed point theory to solve games of imperfect information. The fixed point theory is defined on the lattice of antichains of sets of states. Contrary to the classical solution proposed by Reif [Rei84], our new solution does not involve determinization. As a consequence, it is readily applicable to classes of systems that do not… (More)

Timed automata are governed by an idealized semantics that assumes a perfectly precise behavior of the clocks. The traditional semantics is not robust because the slightest perturbation in the timing of actions may lead to completely different behaviors of the automaton. Following several recent works, we consider a relaxation of this semantics, in which… (More)

In a former paper, we defined a new semantics for timed automata, the Almost ASAP semantics, which is parameterized by ∆ to cope with the reaction delay of the controller. We showed that this semantics is implementable provided there exists a strictly positive value for the parameter ∆ for which the strategy is correct. In this paper, we define the… (More)

We consider two-player parity games with imperfect information in which strategies rely on observations that provide imperfect information about the history of a play. To solve such games, i.e., to determine the winning regions of players and corresponding winning strategies, one can use the subset construction to build an equivalent perfect-information… (More)

The linear temporal logic (LTL) was introduced by Pnueli as a logic to express properties over the computations of reactive systems. Since this sem-inal work, there have been a large number of papers that have studied deductive systems and algorithmic methods to reason about the correctness of reactive programs with regard to LTL properties. In this paper,… (More)

Alpaga is a solver for two-player parity games with imperfect information. Given the description of a game, it determines whether the first player can ensure to win and, if so, it constructs a winning strategy. The tool provides a symbolic implementation of a recent algorithm based on antichains.

Recently we have proposed the " almost ASAP " semantics as an alternative semantics for timed automata. This semantics is useful when modeling real-time controllers : control strategies modeled with this semantics are robust and implementable (without making the syn-chrony hypothesis). We show in this paper how to effectively encode this semantics using… (More)