Negotiation is an interaction that happens in multi-agent systems when agents have conflicting objectives and must look for an acceptable agreement. A typical negotiating situation involves two agents that cannot reach their goals by themselves because they do not have some resources they need or they do not know how to use them to reach their goals. Therefore, they must start a negotiation dialogue, taking also into account that they might have incomplete or wrong beliefs about the other agent's goals and resources. This article presents a negotiating agent model based on argumentation, which is used by the agents to reason on how to exchange resources and knowledge in order to achieve their goals. Agents that negotiate have incomplete beliefs about the others, so that the exchange of arguments gives them information that makes it possible to update their beliefs. In order to formalize their proposals in a negotiation setting, the agents must be able to generate, select and evaluate arguments associated with such offers, updating their mental state accordingly. In our approach, we will focus on an argumentation-based negotiation model between two cooperative agents. The arguments generation and interpretation process is based on belief change operations (expansions, contractions and revisions), and the selection process is a based on a strategy. This approach is presented through a high-level algorithm implemented in logic programming. We show various theoretical properties associated with this approach, which have been formalized and proved using Coq, a formal proof management system. We also illustrate, through a case study, the applicability of our approach in order to solve a slightly modified version of the well-known home improvement agents problem. Moreover, we present various simulations that allow assessing the impact of belief revision on the negotiation process.
Abstract. The importance of negotiation has increased in the last years as a relevant interaction to solve conflicts in multiagent systems. Although there are many different scenarios, a typical negotiating situation involves two cooperative agents that cannot reach their goals by themselves because they do not have some resources needed to reach such goals. Therefore, a way to improve their mutual benefit is to start a negotiation dialogue, taking into account that they might have incomplete or incorrect beliefs about the other agent's goals and resources. The exchange of arguments during the negotiation gives them information that makes it possible to update their beliefs and consequently they can offer proposals which are closer for reaching a deal. In order to formalize their proposals in a negotiation setting, the agents must be able to generate, select and evaluate arguments associated with such offers, updating their mental state accordingly. We situate our work on this kind of scenarios with two argumentation-based negotiation agents equipped with belief revision operations in the generation and interpretation of arguments. It has been proved that those agents that take advantage of belief revision during the negotiation achieve an overall better performance. Because the belief revision process depends on the information the agents exchange in their utterances, in this paper we focus on different communication strategies the agents may implement and the impact that they have in the negotiation process. For this purpose, we present a negotiation protocol where the messages are extended to include a critique to the last proposal received and a counterproposal. Also, we define proposals that may be more or less informative containing different justifications. An intentional agent architecture is proposed and following this model different kind of negotiating agents are created using diverse communication strategies. To assess the impact these strategies have in the negotiation process some simulations are conducted, analyzing the results obtained.
This paper presents a novel approach to the well-known Knapsack problem, extending it as a bilateral negotiating problem with default information where each of the two agents has a knapsack and there is a set of items distributed between them. The agents can exchange items in order to reach their goal: fill their knapsacks with items without exceeding their capacity with the aim of maximizing their utility function. Initially the agents do not have any information about their counterpart, e.g. the exact weight of their items and their associated values, so that they consider default assignments for them. This default information can change as the negotiation progresses. A sequential negotiation protocol is proposed, along with different strategies of information exchange and the results obtained when the agents negotiate using them. Information transfer efficiency is assessed in terms of the overall usefulness, quantity of information disclosed and negotiation duration.
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