Abstract
Negotiation plays a fundamental role in systems composed of multiple autonomous agents. Some negotiations may require a more elaborated dialogue where agents would explain offer rejections in a general and vague way. We propose that agents would represent their disappointment about an offer through fuzzy logic. Fuzzyness can also be very useful in order to make human-like negotiations, consequently, user profiles may become more difficult to acquire in detail. Specifically we study two alternatives: a piece-wise fuzzy set or a linguistic label applied to each attribute of the offer. These alter-natives are evaluated comparing the performance of both types of counter-offers with a classical approach based on linear programming. Therefore, the average of negotiation length, benefits and percentage of agreements allow us to conclude the accuracy of the alternatives proposed.