The inability to have a complete description of a situation is often a limitation in the use of computer systems in decision processes. To overcome this limitation, the paper proposes using defeasible logic for persuasion dialogues. In defeasible logic, conclusions can be strict or defeasible; defeasible conclusions are tentative conclusions that can be retracted when new information becomes available. The logic is extended to incorporate the beliefs and the knowledge of the agents involved in a dialogue. Different kinds of dialogues are possible depending on preconditions obtained from the mental states of the agents, and protocols for some types of dialogues are presented (for example, explanation and persuasion dialogues).

The paper addresses an important topic, but it suffers from some drawbacks: the mechanisms of defeasible logic are not presented in the paper, so readers not familiar with this logic are not able to fully understand the protocols for dialogues. The whole idea of the paper is based on the mental attitudes (beliefs and knowledge) of the agents, but it does not specify how these are handled by the logic; the authors admit that this is a matter for further work.