Aims

Multi-Agent Systems (MAS) are a natural setting for conflicts where different perspectives regarding shared information are generated by the different agents. The multiple conflicting perspectives can be: (i) incompatible beliefs regarding some shared concept, or (ii) reconcilable beliefs regarding some shared concept. These types of conflicts are called, respectively, negative and positive conflicts. The aim of this project was the development of methodologies for solving conflicting beliefs. The type of MAS envisaged are made of autonomous cooperating agents with belief revision capabilities. In particular, the agents implemented are built upon individual Assumption based Truth Maintenance Systems (ATMS) enhanced with the necessary abilities to perform conflict resolution. Each agent has a self model, where the agent's individual intelligent system is described (knowledge and beliefs that the agent has or is expected to have), and an acquaintances model, where the full listing of the capabilities of the other agents which are relevant to the problem solving activity of the agent is provided (tasks and results that the other agents are expected to provide or share with the agent). It is based on the information listed on the acquaintances model that the agents cooperate, performing task sharing and result sharing. The investigation carried out was focussed on building conflict solving methodologies for two specific kinds of negative conflicts:

1. Context Independent Conflicts - when some agents believe while some other do not believe in the same information item;

2. Context Dependent Conflicts - when the agents detect incompatible sets of beliefs and have, as a result, to drop previously held conclusions (reason maintenance).

While in the case of Belief/Disbelief conflicts, the methodology for conflict resolution has to decide which belief status should be adopted, in the case of the Context Independent conflicts, it has to try to find alternatives to support the previously believed conclusions.
The concept of conflict resolution addressed in this work is not a one time conflict solving activity as in a typical MAS. A conflict in this scenario is dynamic, may have multiple episodes during its existence, and only ceases to exist when all of the involved agents believe in the proposition. New conflict episodes occur whenever any change regarding the conflict is detected, either because the number of agents involved or because the perspectives themselves have changed. Every time a new episode of an existing conflict is detected a re-evaluation of the conflict is performed and a new outcome may be generated.

Methodologies

Specific methodologies were designed for the resolution of the identified types of negative conflicts (for a detailed description of these methodologies I suggest the reading of the paper "Solving Conflicting Beliefs with a Distributed Belief Revision Approach", Springer Verlag, Lecture Notes in Artificial Intelligence, Vol. 1952):

A methodology for solving Context Independent Conflicts  

- a selection process based on the assessment of the credibility values of the opposing belief status, and

A methodology for solving Context Dependent Conflicts  

- a search process for an unique consensual alternative based on a "next best candidate" strategy.

The dynamic conflict resolution  methodologies developed are supported by distributed belief revision functionalities and argumentation based negotiation protocols. 

Conclusion

The concept of dynamic conflict resolution addressed in this work classifies a conflict as a multiple episode occurrence, which terminates only when all of the involved agents believe in the shared information. New conflict episodes occur whenever any change regarding the conflict is detected, either because the number of agents involved or because the perspectives themselves have changed. Every time a new episode of an existing conflict is detected a re-evaluation of the conflict is performed, the previous episode result is dropped and a the new episode outcome is generated.
Although the conflicts addressed may be considered specific of the proposed framework, the methodologies developed are general and can be applied to more general kinds of conflicts. On one hand, the Context Independent conflicts represent the negative type of conflicts where a fundamented choice between two opposite results has to be made, while on the other hand, the Context Dependent Conflicts are a negative type of conflict (resulted from the detection of a set of invalid beliefs) where the solution lays on the search for an alternative consensus. The search for a consensus is a well suited methodology for the general type of negative conflicts, especially when more than two irreconcilable perspectives are in conflict - the involved agents try to find alternative support for believing in an unique perspective.
The implemented methodologies try to solve the detected conflicts but cannot, beforehand, guarantee whether their effort will be successful or not.