Logical Foundations of Negotiation: Outcome, Concession, and Adaptation

Abstract

Most theoretical investigations of the process of negotiation between agents have, thus far, been quantitative in nature. This paper is a contribution towards the body of literature which views negotiation in a qualititative light. Our aim is to provide a logical framework for describing a process of negotiation between agents. We assume that agents are rational, cooperative and truthful. Based on this we provide a characterisation of the rational outcomes of a process of negotiation in terms of a set of rationality postulates, as well as a method for constructing exactly the rational outcomes. The framework is extended by describing two modes of negotiation from which an outcome can be reached. In the concessionary mode, agents are required to weaken their demands in order to accommodate the demands of 1 others. The outcome of such a concessionary process is obtained by combining the (weakened) demands of all agents. In the adaptationist mode, agents are required to adapt to the demands of other in some appropriate fashion. In this case, the outcome consists of the adapted demands that all agents have in common. Both concession and adaptation are alos characterised in terms of rationality postulates. We also provide methods for constructing exactly the rational concessions, as well as the rational adaptations. The central result of the paper is the observation that the outcomes obtained from the concessionary and adaptationist modes both correspond exactly to the rational outcomes. We conclude by pointing out the links between negotiation and AGM belief change, and providing a glimpse of how this may be used to define a notion of preference-based negotiation. 1