Preface to the special issue on GandALF 2012

Electronic Proceedings in Theoretical Computer Science, 2013

2016

This work is dedicated to the public domain. The discrete strategy improvement algorithm for parity games and complexity measures for directed graphs

2001

Abstract. The automata-theoretic approach to linear temporal logic uses the theory of automata as a unifying paradigm for program specification, verification, and synthesis. Both programs and specifications are in essence descriptions of computations. These computations can be viewed as words over some alphabet. Thus, programs and specifications can be viewed as descriptions of languages over some alphabet.

Game-Theoretic Automata (GTA) unify game theory and automata theory into a single framework, enabling rigorous formalization of sequential games. By leveraging temporal logic, state transitions, and explicit strategy modeling, GTA is both expressive and computationally tractable for a wide range of games. In this paper, we build on established formalisms, including the FuturLang approach to encoding strategic interactions, and introduce a series of open problems-formalized as conjectured theorems-that chart a path toward a deeper theoretical understanding of GTAs. We highlight directions that have broad implications across game theory, automata theory, and AI.

Journal of Logic and Computation, 2009

The Game Description Language (GDL) is a special purpose declarative language for defining games. GDL is used in the AAAI General Game Playing Competition, which tests the ability of computer programs to play games in general, rather than just the ability to play a specific game. Participants in the competition are provided with a previously unknown game specified in GDL, and are required to dynamically and autonomously determine how best to play this game. Recently, there has been much interest in the use of strategic cooperation logics for reasoning about game-like scenarios-the Alternating-time Temporal Logic (ATL) of Alur, Henzinger, and Kupferman is perhaps the best known example. Such logics are specifically intended to support reasoning about game-theoretic properties of multi-agent systems. In short, the aim of this article is to make a concrete link between ATL and GDL, with the ultimate goal of using ATL to reason about GDL-specified games. We make the following contributions. First, we demonstrate that GDL can be understood as a specification language for ATL models, and prove that the problem of interpreting ATL formulae over propositional GDL descriptions is EXPTIME-complete. Second, we use ATL to characterize a class of 'fair playability' conditions, which might or might not hold of various games.

2010

The seminar took place from 20th until 25th June 2010. Its primary aim was to foster interaction between researchers working on modelling programs/proofs using games and the verification community. The meeting brought together 28 researchers from eight different countries, both junior and senior, for a systematic assessment of what the two areas have to offer to one another, critical evaluation of what has been achieved so far, with a view to establishing common research goals for the future.

Electronic Notes in Theoretical Computer Science, 2006

3-valued models have been advocated as a means of system abstraction such that verifications and refutations of temporal-logic properties transfer from abstract models to the systems they represent. Some application domains, however, require multiple models of a concrete or virtual system. We build the mathematical foundations for 3-valued property verification and refutation applied to sets of common concretizations of finitely many models. We show that validity checking for the modal mu-calculus has the same cost (EXPTIME-complete) on such sets as on the set of all 2-valued models, provide an efficient algorithm for checking whether common concretizations exist for a fixed number of models, and propose using parity games on variants of tree automata to efficiently approximate validity checks of multiple models. Structural properties of a universal topological model confirm that such approximations are reasonably precise only for tree-automata-like models.

Bull. EATCS, 2020

The solution of games is a key decision problem in the context of verification of open systems and program synthesis. We present an automata-theoretic approach to solve timed games. Our solution gives a general framework to solve many classes of timed games via a translation to tree automata, extending to timed games a successful approach to solve discrete games. Our approach relies on translating a timed automaton into a tree automaton that accepts all the trees corresponding to a given strategy of the protagonist. This construction exploits the region automaton introduced by Alur and Dill. We use our framework to solve timed Büchi games in exponential time, timed Rabin games in exponential time, Ctl games in exponential time and Ltl games in doubly exponential time. All these results are tight in the sense that they match the known lower bounds on these decision problems.

Computer Science Logic, 2006

Game quantification is an expressive concept and has been studied in model theory and descriptive set theory, especially in relation to infinitary logics. Automatic structures on the other hand appear very often in computer science, especially in program verification. We extend first-order logic on structures on words by allowing to use an infinite string of alternating quantifiers on letters of a word, the game quantifier. This extended logic is decidable and preserves regularity on automatic structures, but can be undecidable on other structures even with decidable first-order theory. We show that in the presence of game quantifier any relation that allows to distinguish successors is enough to define all regular relations and therefore the game quantifier is strictly more expressive than first-order logic in such cases. Conversely, if there is an automorphism of atomic relations that swaps some successors then we prove that it can be extended to any relations definable with game quantifier. After investigating it's expressiveness, we use game quantification to introduce a new type of combinatorial games with multiple players and imperfect information exchanged with respect to a hierarchical constraint. It is shown that these games on finite arenas exactly capture the logic with game quantifier when players alternate their moves but are undecidable and not necessarily determined in the other case. In this way we define the first model checking games with finite arenas that can be used for model checking first-order logic on automatic structures.