Recoverable Cuts to Make Agreement among Peers

In peer-to-peer (P2P) applications, peers make an agreement on one opinion. Agreement procedures have to be so flexible that persons can change their opinions. We discuss a flexible agreement protocol of multiple peers by taking advantage of human behaviors in a fully unstructured P2P network. There are forward, backward, mining, and observation strategies for each peer to find a value to make an agreement. In the forward strategy, a peer shows a new value to the other peers. In the backward one, a peer backs to a previous round. In order to back to the previous round, values taken after the round have to be withdrawn. In the mining one, a peer tries to find a tuple of previous values named a cut which satisfies the agreement condition. In the observation one, a peer does not take a new value. Since each peer autonomously takes one of the strategies at each round, the peers might take inconsistent strategies. For example, only if every peer takes the mining strategy, the mining strategy can be adopted. The mining strategy is inconsistent with the others. The peers have to do negotiation with each other to take consistent strategies. We discuss how peers cooperate to take consistent strategies at each round.