Laurent Perrussel

Prime forms and minimal change in propositional belief bases

This paper proposes to use prime implicants and prime implicates normal forms to represent belief sets. This representation is used, on the one hand, to define syntactical versions of belief change operators that also satisfy the rationality postulates but present better complexity properties than those proposed in the literature and, on the other hand, to propose a new minimal distance that adopts as a minimal belief unit a “fact”, defined as a prime implicate of the belief set, instead of the usually adopted Hamming distance, i.e., the number of propositional symbols on which the models differ. Some experiments are also presented that show that this new minimal distance allows to define belief change operators that usually preserve more information of the original belief set.

Mechanism design for double auctions with temporal constraints

This paper examines an extended double auction model where market clearing is restricted by temporal constraints. It is found that the allocation problem in this model can be effectively transformed into a weighted bipartite matching in graph theory. By using the augmentation technique, we propose a Vickrey-Clarke-Groves (VCG) mechanism in this model and demonstrate the advantages of the payment compared with the classical VCG payment (the Clarke pivot payment). We also show that the algorithms for both allocation and payment calculation run in polynomial time. It is expected that the method and results provided in this paper can be applied to the design and analysis of dynamic double auctions and futures markets.

Maximal Matching for Double Auction

We study the problem of mechanism design for a double auction market where multiple buyers and sellers buy and sell a commodity. We design and implement a matching algorithm that maximizes market liquidity, including the number of transactions and buy/sell-volume. We prove that, given the number of matches, the algorithm also maximizes auctioneer’s profit. Based on the CAT Tournament (Trading Agent Competition Market Design) platform, we show with experiments that the new matching method not only increases market liquidity but also significantly improves market share and auctioneer’s profit in the long term, compared with equilibrium matching, the most commonly used matching method.

Trust-based belief change

We propose a modal logic that supports reasoning about trust-based belief change. The term trust-based belief change refers to belief change that depends on the degree of trust the receiver has in the source of information.

A modal framework for relating belief and signed information

The aim of this paper is to propose a modal framework for reasoning about signed information. This modal framework allows agents to keep track of information source as long as they receive information in a multi-agent system. Agents gain that they can elaborate and justify their own current belief state by considering a reliability relation over the sources of information. The belief elaboration process is considered under two perspectives: (i) from a static point of view an agent aggregates received signed information according to its preferred sources in order to build its belief and (ii) from a dynamic point of view as an agent receives information it adapts its belief state about signed information. Splitting the notions of beliefs and signed statement is useful for handling the underlying trust issue: an agent believes some statement because it may justify the statements origin and its reliability.

Mediation using m -states

Model-based propositional belief merging operators are constructed from distances between the interpretations, or states, of the logic under consideration. In this paper we extend the notion of a distance between interpretations to generalised versions of propositional interpretations referred to as m-states. m-states allow for the definition of m-merging operators, which are generalisations of classical model-based merging operators. We show how m-merging, combined with appropriate measures of satisfaction, can be used to construct a logical framework for agent mediation: a process of intervening between parties with conflicting demands to facilitate a compromise.

A Logical Approach for Describing (Dis)Belief Change and Message Processing

This paper focuses on the features of two KQML performatives, namely tell and untell, in the context of nonprioritized belief change. Tell allows agents to send beliefs while untell allows agents to send explicit disbeliefs. In a multi agent system, agents have to change their belief when they receive new information from other agents. They may revise or contract their belief state accordingly. The revision action consists of inserting a new belief in a beliefs set while the contraction action consists of managing a set of disbeliefs. Whenever incoming information entails inconsistencies in an agentýs belief state, the agent must either drop some beliefs or refuse the incoming statement. For this, agents consider a preference relation over other agents embedded in the multi agent system and may reject new information based on their belief state and their preference relation. In this article, we survey a logic-based framework for handling messages and (dis)beliefs change. In this context, we formally describe the consequences of tell and untell performatives.

A persuasion dialog for gaining access to information

This paper presents a formal protocol for agents engaged in argumentation over access to information sources. Obtaining relevant information is essential for agents engaged in autonomous, goal-directed behavior, but access to such information is usually controlled by other autonomous agents having their own goals. Because these various goals may be in conflict with one another, rational interactions between the two agents may take the form of a dialog, in which requests for information are successively issued, considered, justified and criticized. Even when the agents involved in such discussions agree on all the arguments for and the arguments against granting access to some information source, they may still disagree on their preferences between these arguments. To represent such situations, we design a protocol for dialogs between two autonomous agents for seeking and granting authorization to access some information source. This protocol is based on an argumentation dialog where agents handle specific preferences and acceptability over arguments. We show how this argumentation framework provides a semantics to the protocol dedicated to the exchange of arguments, and we illustrate the proposed framework with an example in medicine.

Experimental Market Mechanism Design for Double Auction

In this paper, we introduce an experimental approach to the design, analysis and implementation of market mechanisms based on double auction. We define a formal market model that specifies the market policies in a double auction market. Based on this model, we introduce a set of criteria for the evaluation of market mechanisms. We design and implement a set of market policies and test them with different experimental settings. The results of experiments provide us a better understanding of the interrelationship among market policies and also show that an experimental approach can greatly improve the efficiency and effectiveness of market mechanism design.

On Hierarchical Task Networks

In planning based on hierarchical task networks (HTN), plans are generated by refining high-level actions (‘compound tasks’) into lower-level actions, until primitive actions are obtained that can be sent to execution. While a primitive action is defined by its precondition and effects, a high-level action is defined by zero, one or several methods: sets of (high-level or primitive) actions decomposing it together with a constraint. We give a semantics of HTNs in terms of dynamic logic with program inclusion. We propose postulates guaranteeing soundness and completeness of action refinement. We also show that hybrid planning can be analysed in the same dynamic logic framework.