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139Quantified Coalition LogicSynthese 165 (2). 2008.We add a limited but useful form of quantification to Coalition Logic, a popular formalism for reasoning about cooperation in game-like multi-agent systems. The basic constructs of Quantified Coalition Logic (QCL) allow us to express such properties as "every coalition satisfying property P can achieve φ" and "there exists a coalition C satisfying property P such that C can achieve φ". We give an axiomatisation of QCL, and show that while it is no more expressive than Coalition Logic, it is neve…Read more
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136Towards a theory of intention revisionSynthese 155 (2): 265-290. 2007.Although the change of beliefs in the face of new information has been widely studied with some success, the revision of other mental states has received little attention from the theoretical perspective. In particular, intentions are widely recognised as being a key attitude for rational agents, and while several formal theories of intention have been proposed in the literature, the logic of intention revision has been hardly considered. There are several reasons for this: perhaps most importan…Read more
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125Social laws in alternating time: Effectiveness, feasibility, and synthesisSynthese 156 (1): 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 systems. First, we show that the Alternating-time Temporal Logic (atl) of Alur, Henzinger, and Kupferman provides an elegant and powerful framework within which to express and understand social laws for m…Read more
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123Generalized quantifiers and modal logicJournal of Logic, Language and Information 2 (1): 19-58. 1993.We study several modal languages in which some (sets of) generalized quantifiers can be represented; the main language we consider is suitable for defining any first order definable quantifier, but we also consider a sublanguage thereof, as well as a language for dealing with the modal counterparts of some higher order quantifiers. These languages are studied both from a modal logic perspective and from a quantifier perspective. Thus the issues addressed include normal forms, expressive power, c…Read more
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112Everything is Knowable – How to Get to Know Whether a Proposition is TrueTheoria 78 (2): 93-114. 2012.Fitch showed that not every true proposition can be known in due time; in other words, that not every proposition is knowable. Moore showed that certain propositions cannot be consistently believed. A more recent dynamic phrasing of Moore-sentences is that not all propositions are known after their announcement, i.e., not every proposition is successful. Fitch's and Moore's results are related, as they equally apply to standard notions of knowledge and belief (S 5 and KD45, respectively). If we …Read more
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85Multi-Modal CTL: Completeness, Complexity, and an Application (review)Studia Logica 92 (1): 1-26. 2009.We define a multi-modal version of Computation Tree Logic (ctl) by extending the language with path quantifiers E δ and A δ where δ denotes one of finitely many dimensions, interpreted over Kripke structures with one total relation for each dimension. As expected, the logic is axiomatised by taking a copy of a ctl axiomatisation for each dimension. Completeness is proved by employing the completeness result for ctl to obtain a model along each dimension in turn. We also show that the logic is de…Read more
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77Cooperation, knowledge, and time: Alternating-time temporal epistemic logic and its applicationsStudia Logica 75 (1): 125-157. 2003.Branching-time 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 Altern…Read more
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66On the semantics of graded modalitiesJournal of Applied Non-Classical Logics 2 (1): 81-123. 1992.
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61Temporalizing epistemic default logicJournal of Logic, Language and Information 7 (3): 341-367. 1998.We present an epistemic default logic, based on the metaphore of a meta-level architecture. Upward reflection is formalized by a nonmonotonic entailment relation, based on the objective facts that are either known or unknown at the object level. Then, the meta (monotonic) reasoning process generates a number of default-beliefs of object-level formulas. We extend this framework by proposing a mechanism to reflect these defaults down. Such a reflection is seen as essentially having a temporal flav…Read more
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54Editorial Introduction to the Special Issue LOFT SevillaJournal of Philosophical Logic 42 (6): 795-798. 2013.
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53Multi-Modal CTL: Completeness, Complexity, and an ApplicationStudia Logica 92 (1). 2009.We define a multi-modal version of Computation Tree Logic (CTL) by extending the language with path quantifiers $E^\delta $ and $E^\delta $ where δ denotes one of finitely many dimensions, interpreted over Kripke structures with one total relation for each dimension. As expected, the logic is axiomatised by taking a copy of a CTL axiomatisation for each dimension. Completeness is proved by employing the completeness result for CTL to obtain a model along each dimension in turn. We also show that…Read more
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52On agents that have the ability to chooseStudia Logica 66 (1): 79-119. 2000.We demonstrate ways to incorporate nondeterminism in a system designed to formalize the reasoning of agents concerning their abilities and the results of the actions that they may perform. We distinguish between two kinds of nondeterministic choice operators: one that expresses an internal choice, in which the agent decides what action to take, and one that expresses an external choice, which cannot be influenced by the agent. The presence of abilities in our system is the reason why the usual a…Read more
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50Dynamic Epistemic LogicInternet Encyclopedia of Philosophy. 2016.Dynamic Epistemic Logic This article tells the story of the rise of dynamic epistemic logic, which began with epistemic logic, the logic of knowledge, in the 1960s. Then, in the late 1980s, came dynamic epistemic logic, the logic of change of knowledge. Much of it was motivated by puzzles and paradoxes. The number … Continue reading Dynamic Epistemic Logic →
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48Knowledge condition gamesJournal of Logic, Language and Information 15 (4): 425-452. 2006.Understanding the flow of knowledge in multi-agent protocols is essential when proving the correctness or security of such protocols. Current logical approaches, often based on model checking, are well suited for modeling knowledge in systems where agents do not act strategically. Things become more complicated in strategic settings. In this paper we show that such situations can be understood as a special type of game – a knowledge condition game – in which a coalition “wins” if it is able to b…Read more
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45Robust normative systems and a logic of norm complianceLogic Journal of the IGPL 18 (1): 4-30. 2010.Although normative systems, or social laws, have proved to be a highly influential approach to coordination in multi-agent systems, the issue of compliance to such normative systems remains problematic. In all real systems, it is possible that some members of an agent population will not comply with the rules of a normative system, even if it is in their interests to do so. It is therefore important to consider the extent to which a normative system is robust, i.e., the extent to which it remain…Read more
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45Honesty in partial logicStudia Logica 56 (3): 323-360. 1996.We propose an epistemic logic in which knowledge is fully introspective and implies truth, although truth need not imply epistemic possibility. The logic is presented in sequential format and is interpreted in a natural class of partial models, called balloon models. We examine the notions of honesty and circumscription in this logic: What is the state of an agent that 'only knows φ' and which honest φ enable such circumscription? Redefining stable sets enables us to provide suitable syntactic a…Read more
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42A general approach to multi-agent minimal knowledge: With tools and SamplesStudia Logica 72 (1): 61-84. 2002.We extend our general approach to characterizing information to multi-agent systems. In particular, we provide a formal description of an agent''s knowledge containing exactly the information conveyed by some (honest) formula . Only knowing is important for dynamic agent systems in two ways. First of all, one wants to compare different states of knowledge of an agent and, secondly, for agent a''s decisions, it may be relevant that (he knows that) agent b does not know more than . There are three…Read more
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42Logics for Qualitative Coalitional GamesLogic Journal of the IGPL 17 (3): 299-321. 2009.Qualitative Coalitional Games are a variant of coalitional games in which an agent's desires are represented as goals that are either satisfied or unsatisfied, and each choice available to a coalition is a set of goals, which would be jointly satisfied if the coalition made that choice. A coalition in a QCG will typically form in order to bring about a set of goals that will satisfy all members of the coalition. Our goal in this paper is to develop and study logics for reasoning about QCGs. We b…Read more
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41Nonmonotonic reasoning, Grigoris AntoniouJournal of Logic, Language and Information 9 (1): 125-128. 2000.
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41Seeing is believingJournal of Logic, Language and Information 6 (1): 33-61. 1997.In this paper a formal framework is proposed in which variousinformative actions are combined, corresponding to the different ways in whichrational agents can acquire information. In order to solve the variousconflicts that could possibly occur when acquiring information fromdifferent sources, we propose a classification of the informationthat an agent possesses according to credibility. Based on this classification, we formalize what itmeans for agents to have seen or heard something, or to bel…Read more
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36A Modal Logic for Mixed StrategiesStudia Logica 102 (2): 339-360. 2014.Modal logics have proven to be a very successful tool for reasoning about games. However, until now, although logics have been put forward for games in both normal form and games in extensive form, and for games with complete and incomplete information, the focus in the logic community has hitherto been on games with pure strategies. This paper is a first to widen the scope to logics for games that allow mixed strategies. We present a modal logic for games in normal form with mixed strategies, a…Read more
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35Introduction to the Special Issue on Logic and the Foundations of Game and Decision TheoryStudia Logica 107 (3): 451-455. 2019.
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35Logic for applications, Anil Nerode and Richard A. shoreJournal of Logic, Language and Information 7 (2): 228-229. 1998.
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35Reasoning About Social Choice FunctionsJournal of Philosophical Logic 40 (4): 473-498. 2011.We introduce a logic specifically designed to support reasoning about social choice functions. The logic includes operators to capture strategic ability, and operators to capture agent preferences. We establish a correspondence between formulae in the logic and properties of social choice functions, and show that the logic is expressively complete with respect to social choice functions, i.e., that every social choice function can be characterised as a formula of the logic. We prove that the log…Read more
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33Connecting dynamic epistemic and temporal epistemic logicsLogic Journal of the IGPL 21 (3): 380-403. 2013.
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32Iterated Belief Change in Multi-Agent SystemsLogic Journal of the IGPL 11 (2): 223-246. 2003.We give a model for iterated belief change in multi-agent systems. The formal tool we use for this is a combination of modal and dynamic logic. Two core notions in our model are the expansion of the knowledge and beliefs of an agent, and the processing of new information. An expansion is defined as the change in the knowledge and beliefs of an agent when it decides to believe an incoming formula while holding on to its current propositional beliefs. To prevent our agents from forming inconsisten…Read more
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University of LiverpoolRegular Faculty
Areas of Interest
Epistemology |
Logic and Philosophy of Logic |