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Cooperation, Knowledge, and Time: Alternatingtime Temporal Epistemic Logic and its Applications
 Copyright 2004 ACM
, 2003
"... Branchingtime temporal logics have proved to be an extraordinarily successful tool in the formal specification and verification of distributed systems. Much of their success stems from the tractability of the model checking problem for the branching time logic ctl, which has made it possible to imp ..."
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Cited by 86 (8 self)
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Branchingtime temporal logics have proved to be an extraordinarily successful tool in the formal specification and verification of distributed systems. Much of their success stems from the tractability of the model checking problem for the branching time logic ctl, which has made it possible to implement tools that allow designers to automatically verify that systems satisfy requirements expressed in ctl. Recently, ctl was generalised by Alur, Henzinger, and Kupferman in a logic known as "Alternatingtime Temporal Logic" (atl). The key insight in atl is that the path quantifiers of ctl could be replaced by "cooperation modalities", of the form where # is a set of agents. The intended interpretation of an atl formula is that the agents # can cooperate to ensure that # holds (equivalently, that # have a winning strategy for #). In this paper, we extend atl with knowledge modalities, of the kind made popular in the work of Fagin, Halpern, Moses, Vardi and colleagues. Combining these knowledge modalities with atl, it becomes possible to express such properties as "group # can cooperate to bring about # i# it is common knowledge in # that #". The resulting logic  Alternatingtime Temporal Epistemic Logic (atel)  shares the tractability of model checking with its atl parent, and is a succinct and expressive language for reasoning about gamelike multiagent systems.
Towards a Logic of Rational Agency
, 2003
"... Rational agents are important objects of study in several research communities, including economics, philosophy, cognitive science, and most recently computer science and artificial intelligence. Crudely, a rational agent is an entity that is capable of acting on its environment, and which chooses t ..."
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Cited by 58 (6 self)
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Rational agents are important objects of study in several research communities, including economics, philosophy, cognitive science, and most recently computer science and artificial intelligence. Crudely, a rational agent is an entity that is capable of acting on its environment, and which chooses to act in such a way as to further its own best interests. There has recently been much interest in the use of mathematical logic for developing formal theories of such agents. Such theories view agents as practical reasoning systems, deciding moment by moment which action to perform nexi, given the beliefs they have about the world and their desires with respect to how they would like the world to be. In this article, we survey the state of the art in developing logical theories of rational agency. Following a discussion on the dimensions along which such theories can vary, we briefly survey the logical tools available in order to construct such theories. We then review and critically assess three of the best known theories of rational agency: Cohen and Levesque's intention logic, Rao and Georgeff's BDI logics, and the KARO framework of Meyer et al. We then discuss the various roles that such logics can play in helping us to engineer rational agents, and conclude with a discussion of open problems.
On The Logic Of Cooperation And Propositional Control
, 2005
"... Cooperation logics have recently begun to attract attention within the multiagent systems community. Using a cooperation logic, it is possible to represent and reason about the strategic powers of agents and coalitions of agents in gamelike multiagent systems. These powers are generally assumed t ..."
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Cited by 56 (22 self)
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Cooperation logics have recently begun to attract attention within the multiagent systems community. Using a cooperation logic, it is possible to represent and reason about the strategic powers of agents and coalitions of agents in gamelike multiagent systems. These powers are generally assumed to be implicitly defined within the structure of the environment, and their origin is rarely discussed. In this paper, we study a cooperation logic in which agents are each assumed to control a set of propositional variablesthe powers of agents and coalitions then derive from the allocation of propositions to agents. The basic modal constructs in this Coalition Logic of Propositional Control (CLPC) allow us to express the fact that a group of agents can cooperate to bring about a certain state of affairs. After motivating and introducing CLPC, we provide a complete axiom system for the logic, investigate the issue of characterising control in CLPC with respect to the underlying power structures of the logic, and formally investigate the relationship between CLPC and Pauly's Coalition Logic. We then show that the model checking and satisfiability problems for CLPC are both PSPACEcomplete, and conclude by discussing our results and how CLPC sits in relation to other logics of cooperation.
Coalition games and alternating temporal logics
 Proceeding of the Eighth Conference on Theoretical Aspects of Rationality and Knowledge (TARK VIII
, 2001
"... We draw parallels between coalition game logics developed in [Pauly, 2000b] and [Pauly, 2000c] on one hand, and alternatingtime temporal logics of computations introduced in [Alur et al, 97] on the other. In particular, we show equivalence of their semantics, embedding of coalition game logics int ..."
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Cited by 50 (4 self)
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We draw parallels between coalition game logics developed in [Pauly, 2000b] and [Pauly, 2000c] on one hand, and alternatingtime temporal logics of computations introduced in [Alur et al, 97] on the other. In particular, we show equivalence of their semantics, embedding of coalition game logics into alternatingtime temporal logic, and propose axiomatic systems for these logics. 1
On the Computational Complexity of Qualitative Coalitional Games
 Artificial Intelligence
, 2004
"... We study coalitional games in which agents are each assumed to have a goal to be achieved, and where the characteristic property of a coalition is a set of choices, with each choice denoting a set of goals that would be achieved if the choice was made. Such qualitative coalitional games (QCGs) are a ..."
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Cited by 50 (15 self)
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We study coalitional games in which agents are each assumed to have a goal to be achieved, and where the characteristic property of a coalition is a set of choices, with each choice denoting a set of goals that would be achieved if the choice was made. Such qualitative coalitional games (QCGs) are a natural tool for modelling goaloriented multiagent systems. After introducing and formally defining QCGs, we systematically formulate fourteen natural decision problems associated with them, and determine the computational complexity of these problems. For example, we formulate a notion of coalitional stability inspired by that of the core from conventional coalitional games, and prove that the problem of showing that the core of a QCG is nonempty is D 1 complete. (As an aside, we present what we believe is the first "natural" problem that is proven to be complete for D 2 .) We conclude by discussing the relationship of our work to other research on coalitional reasoning in multiagent systems, and present some avenues for future research.
Social laws in alternating time: Effectiveness, feasibility, and synthesis
 SYNTHESE (2007) 156:1–19
, 2007
"... Since it was first proposed by Moses, Shoham, and Tennenholtz, the social laws paradigm has proved to be one of the most compelling approaches to the offline coordination of multiagent systems. In this paper, we make four key contributions to the theory and practice of social laws in multiagent syst ..."
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Cited by 45 (17 self)
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Since it was first proposed by Moses, Shoham, and Tennenholtz, the social laws paradigm has proved to be one of the most compelling approaches to the offline coordination of multiagent systems. In this paper, we make four key contributions to the theory and practice of social laws in multiagent systems. First, we show that the Alternatingtime Temporal Logic (atl) of Alur, Henzinger, and Kupferman provides an elegant and powerful framework within which to express and understand social laws for multiagent systems. Second, we show that the effectiveness, feasibility, and synthesis problems for social laws may naturally be framed as atl model checking problems, and that as a consequence, existing atl model checkers may be applied to these problems. Third, we show that the complexity of the feasibility problem in our framework is no more complex in the general case than that of the corresponding problem in the Shoham–Tennenholtz framework (it is npcomplete). Finally, we show how our basic framework can easily be extended to permit social laws in which constraints on the legality or otherwise of some action may be explicitly required. We illustrate the concepts and techniques developed by means of a running example.
Reasoning About Strategies
 In IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science’10, LIPIcs 8
, 2010
"... In open systems verification, to formally check for reliability, one needs an appropriate formalism to model the interaction between open entities and express that the system is correct no matter how the environment behaves. An important contribution in this context is given by modal logics for stra ..."
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Cited by 40 (19 self)
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In open systems verification, to formally check for reliability, one needs an appropriate formalism to model the interaction between open entities and express that the system is correct no matter how the environment behaves. An important contribution in this context is given by modal logics for strategic ability, in the setting of multiagent games, such as ATL, ATL*, and the like. Recently, Chatterjee, Henzinger, and Piterman introduced Strategy Logic, which we denote here by SLCHP, with the aim of getting a powerful framework for reasoning explicitly about strategies. SLCHP is obtained by using firstorder quantifications over strategies and it has been investigated in the specific setting of twoagents turnedbased game structures where a nonelementary modelchecking algorithm has been provided. While SLCHP is a very expressive logic, we claim that it does not fully capture the strategic aspects of multiagent systems. In this paper, we introduce and study a more general strategy logic, denoted SL, for reasoning about strategies in multiagent concurrent systems. We prove that SL strictly includes SLCHP, while maintaining a decidable modelchecking problem. Indeed, we show that it is 2EXPTIMECOMPLETE, thus not harder than that for ATL * and a remarkable improvement of the same problem for SLCHP. We also consider the satisfiability problem and show that it is undecidable already for the sublogic SLCHP under the concurrent game semantics. Digital Object Identifier 10.4230/LIPIcs.FSTTCS.2010.133 1
Alternatingtime temporal logics with irrevocable strategies
 In Proceedings of the 11th Conference on Theoretical Aspects of Rationality and Knowledge (TARK’07
"... In Alternatingtime Temporal Logic (atl), one can express statements about the strategic ability of an agent (or a coalition of agents) to achieve a goal φ such as: “agent i can choose a strategy such that, if i follows this strategy then, no matter what other agents do, φ will always be true”. Howe ..."
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Cited by 38 (9 self)
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In Alternatingtime Temporal Logic (atl), one can express statements about the strategic ability of an agent (or a coalition of agents) to achieve a goal φ such as: “agent i can choose a strategy such that, if i follows this strategy then, no matter what other agents do, φ will always be true”. However, strategies in atl are revocable in the sense that in the evaluation of the goal φ the agent i is no longer restricted by the strategy she has chosen in order to reach the state where the goal is evaluated. In this paper we consider alternative variants of atl where strategies, on the contrary, are irrevocable. The difference between revocable and irrevocable strategies shows up when we consider the ability to achieve a goal which, again, involves (nested) strategic ability. Furthermore, unlike in the standard semantics of atl, memory plays an essential role in the semantics based on irrevocable strategies. 1
Comparing semantics of logics for multiagent systems
 Synthese
"... Abstract. We draw parallels between several closely related logics that combine { in dierent proportions { elements of game theory, computation tree logics, and epistemic logics to reason about agents and their abilities. These are: the coalition game logics CL and ECL introduced by Pauly in 2000, t ..."
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Cited by 38 (14 self)
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Abstract. We draw parallels between several closely related logics that combine { in dierent proportions { elements of game theory, computation tree logics, and epistemic logics to reason about agents and their abilities. These are: the coalition game logics CL and ECL introduced by Pauly in 2000, the alternatingtime temporal logic ATL developed by Alur, Henzinger and Kupferman between 1997 and 2002, and the alternatingtime temporal epistemic logic ATEL by van der Hoek and Wooldridge (2002). In particular, we establish some subsumption and equivalence results for their semantics, as well as interpretation of the alternatingtime temporal epistemic logic into ATL. The focus in this paper is on models: alternating transition systems, multiplayer game models (alias concurrent game structures) and coalition eectivity models turn out to be intimately related, while alternating epistemic transition systems share much of their philosophical and formal apparatus. Our approach is constructive: we present ways to transform between dierent types of models and languages.
PSPACE bounds for rank 1 modal logics
 IN LICS’06
, 2006
"... For lack of general algorithmic methods that apply to wide classes of logics, establishing a complexity bound for a given modal logic is often a laborious task. The present work is a step towards a general theory of the complexity of modal logics. Our main result is that all rank1 logics enjoy a sh ..."
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Cited by 36 (19 self)
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For lack of general algorithmic methods that apply to wide classes of logics, establishing a complexity bound for a given modal logic is often a laborious task. The present work is a step towards a general theory of the complexity of modal logics. Our main result is that all rank1 logics enjoy a shallow model property and thus are, under mild assumptions on the format of their axiomatisation, in PSPACE. This leads to a unified derivation of tight PSPACEbounds for a number of logics including K, KD, coalition logic, graded modal logic, majority logic, and probabilistic modal logic. Our generic algorithm moreover finds tableau proofs that witness pleasant prooftheoretic properties including a weak subformula property. This generality is made possible by a coalgebraic semantics, which conveniently abstracts from the details of a given model class and thus allows covering a broad range of logics in a uniform way.