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Weak Alternating Timed Automata

Pawel Parys ; Igor Walukiewicz.

Alternating timed automata on infinite words are considered. The main result is a characterization of acceptance conditions for which the emptiness problem for these automata is decidable. This result implies new decidability results for fragments of timed temporal logics. It is also shown that,&nbsp;[&hellip;]

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Wreath Products of Forest Algebras, with Applications to Tree Logics

Mikolaj Bojanczyk ; Igor Walukiewicz ; Howard Straubing.

We use the recently developed theory of forest algebras to find algebraic characterizations of the languages of unranked trees and forests definable in various logics. These include the temporal logics CTL and EF, and first-order logic over the ancestor relation. While the characterizations are in&nbsp;[&hellip;]

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Using models to model-check recursive schemes

Sylvain Salvati ; Igor Walukiewicz.

We propose a model-based approach to the model checking problem for recursive schemes. Since simply typed lambda calculus with the fixpoint operator, lambda-Y-calculus, is equivalent to schemes, we propose the use of a model of lambda-Y-calculus to discriminate the terms that satisfy a given&nbsp;[&hellip;]

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A lower bound on web services composition

Anca Muscholl ; Igor Walukiewicz.

A web service is modeled here as a finite state machine. A composition problem for web services is to decide if a given web service can be constructed from a given set of web services; where the construction is understood as a simulation of the specification by a fully asynchronous product of the&nbsp;[&hellip;]

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Positional Determinacy of Games with Infinitely Many Priorities

Erich Graedel ; Igor Walukiewicz.

We study two-player games of infinite duration that are played on finite or infinite game graphs. A winning strategy for such a game is positional if it only depends on the current position, and not on the history of the play. A game is positionally determined if, from each position, one of the two&nbsp;[&hellip;]

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Typing weak MSOL properties

Sylvain Salvati ; Igor Walukiewicz.

We consider lambda-Y-calculus as a non-interpreted functional programming language: the result of the execution of a program is its normal form that can be seen as the tree of calls to built-in operations. Weak monadic second-order logic (wMSOL) is well suited to express properties of such trees. We&nbsp;[&hellip;]

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Soundness in negotiations

Javier Esparza ; Denis Kuperberg ; Anca Muscholl ; Igor Walukiewicz.

Negotiations are a formalism for describing multiparty distributed cooperation. Alternatively, they can be seen as a model of concurrency with synchronized choice as communication primitive. Well-designed negotiations must be sound, meaning that, whatever its current state, the negotiation can still&nbsp;[&hellip;]

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