A belief revision approach for argumentation-based negotiation agents

Abstract

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.

Assessing communication strategies in argumentation-based negotiation agents equipped with belief revision1

“…We model the negotiating agents as intentional ones, following the general architecture presented in [24], but making different improvements in the agents' decision making apparatus to generate, evaluate and interpret more complex utterances. Each agent will have in his mental state, knowledge about his resources (objects and plans) and goals, as well as beliefs on the other agent's resources and goals.…”

“…In this section, following the approach presented in [24] we implement belief revision in ABN agents to improve two important issues in the negotiation: the proposal generation and proposal interpretation. All the information contained in an incoming proposal is used by an agent to revise his beliefs about his counterpart and then, by having more accurate beliefs, the agent can make proposals that are more likely to be accepted.…”

“…All the information contained in an incoming proposal is used by an agent to revise his beliefs about his counterpart and then, by having more accurate beliefs, the agent can make proposals that are more likely to be accepted. The authors showed in [24] that the negotiating agents that implement complete belief revision in these processes (i.e., proposal interpretation and generation) led the negotiation to have better results. In our current work we have improved this agent model equipped with belief revision to be capable of generating and interpreting more complex utterances and we focus our research on the impact that different communication strategies has in the negotiation process.…”

“…These notions were formalized through the definitions of solutions and belief of solutions (Definitions 4.5 and 4.8). To generate the arguments an agent can give to his counterpart, we define the function Gen that was firstly introduced in [24] but for our negotiation model we implement it with some necessary adaptations. This function allows to compute the proposals that are solution to Ag i (i.e., (prop) ∈ S i ) and to compute proposals that are potential solutions for Ag j (i.e., (prop) ∈ B i S j ).…”

“…As the agents initially may have incomplete or incorrect beliefs about the other agent's goals and resources, during the negotiation process they update their beliefs and consequently, their mental state, according to the arguments exchanged. Thus, in the context of the ABN framework previously described, we will follow the belief revision approach for both argument interpretation and argument generation proposed in [24], where we analyzed the impact of including belief revision for improving the overall negotiation process.…”