Negotiation can be conceived as the exchange of messages among self-interested agents in order to settle on an agreement over a given issue. They decide which messages to send according to their preferences and their evolving beliefs. Agents able to handle this dynamics of messages and beliefs can be represented by means of Defeasible Logic Programming augmented with utility functions. This approach to argumentation has the advantage of providing a useful platform for the representation of beliefs and the generation of messages. The interactive nature of negotiations requires an updating mechanism to be applied over the knowledge bases of the agents. The features of this mechanism are described by a
of a negotiation. Although there are many possible protocols, we concentrate on one that ensures the existence of an agreement in negotiations. The formalism of DeLP provides a very natural approach to the characterization of such a protocol.