CP-nets and Nash equilibria

We relate here two formalisms that are used for different purposes in reasoning about multi-agent systems. One of them are strategic games that are used to capture the idea that agents interact with each other while pursuing their own interest. The other are CP-nets that were introduced to express qualitative and conditional preferences of the users and which aim at facilitating the process of preference elicitation. To relate these two formalisms we introduce a natural, qualitative, extension of the notion of a strategic game. We show then that the optimal outcomes of a CP-net are exactly the Nash equilibria of an appropriately defined strategic game in the above sense. This allows us to use the techniques of game theory to search for optimal outcomes of CP-nets and vice-versa, to use techniques developed for CP-nets to search for Nash equilibria of the considered games.Comment: 6 pages. in: roc. of the Third International Conference on Computational Intelligence, Robotics and Autonomous Systems (CIRAS '05). To appea

Global model checking on pushdown multi-agent systems

Pushdown multi-agent systems, modeled by pushdown game structures (PGSs), are an important paradigm of infinite-state multi-agent systems. Alternating-time temporal logics are well-known specification formalisms for multi-agent systems, where the selective path quantifier is introduced to reason about strategies of agents. In this paper, we investigate model checking algorithms for variants of alternating-time temporal logics over PGSs, initiated by Murano and Perelli at IJCAI'15. We first give a triply exponential-time model checking algorithm for ATL* over PGSs. The algorithm is based on the saturation method, and is the first global model checking algorithm with a matching lower bound. Next, we study the model checking problem for the alternating-time mu-calculus. We propose an exponential-time global model checking algorithm which extends similar algorithms for pushdown systems and modal mu-calculus. The algorithm admits a matching lower bound, which holds even for the alternation-free fragment and ATL

Reasoning about resource-bounded multi-agent systems

The thesis presents logic-based formalisms for modelling and reasoning about resource-bounded multi-agent systems. In the field of multi-agent system, it is well-known that temporal logics such as CTL and ATL are powerful tools for reasoning about multi-agent systems. However, there is no natural way to utilise these logics for expressing and reasoning about properties of multi-agent systems where actions of agents require resources to be able to perform. This thesis extends logics including Computational Tree Logic (CTL), Coalition Logic (CL) and Alternating-time Temporal Logic (ATL) which have been used to reasoning about multi-agent systems so that the extended ones have the power to specify and to reason about properties of resource-bounded multi-agent systems. While the extension of CTL is adapted for specifying and reasoning about properties of systems of resource-bounded reasoners where the resources are explicitly memory, communication and time, the extensions of CL and ATL are generalised so that any resource-bounded multi-agent system can be modelled, specified and reasoned about. For each of the logics, we describe the range of resource-bounded multi-agent systems they can account for and axiomatisation systems for reasoning which are proved to be sound and complete. Moreover, we also study the satisfiability problem of these logics

Belief, Knowledge, Lies and Other Utterances in an Algebra for Space and Extrusion

International audienceThe notion of constraint system (cs) is central to declarative formalisms from concurrency theory such as process calculi for concurrent constraint programming (ccp). Constraint systems are often represented as lattices: their elements, called constraints, represent partial information and their order corresponds to entailment. Recently a notion of n-agent spatial cs was introduced to represent information in concurrent constraint programs for spatially distributed multi-agent systems. From a computational point of view a spatial constraint system can be used to specify partial information holding in a given agent's space (local information). From an epistemic point of view a spatial cs can be used to specify information that a given agent considers true (beliefs). Spatial constraint systems, however, do not provide a mechanism for specifying the mobility of information/processes from one space to another. Information mobility is a fundamental aspect of concurrent systems. In this article we develop the theory of spatial constraint systems with operators to specify information and processes moving from a space to another. We shall investigate the properties of this new family of constraint systems and illustrate their applications. From a computational point of view the new operators provide for process/information extrusion, a central concept in formalisms for mobile communication. From an epistemic point of view extrusion corresponds I to a notion we shall call utterance; a piece of information that an agent communicate to others but that may be inconsistent with the agent's beliefs. Utterances can then be used to express instances of epistemic notions such as hoaxes or intentional lies which are common place in social media. Spatial constraint system can express the epistemic notion of belief by means of space functions that specify local information. We shall also show that spatial constraint can also express the epistemic notion of knowledge by means of a derived spatial operator that specifies global information

Computational Models for Normative Multi-Agent Systems

This chapter takes a closer look at computational logic approaches for the design, verification and the implementation of normative multi-agent systems. After a short overview of existing formalisms, architectures and implementation languages, an overview of current research challenges is provided