Contract Net Protocol Sample Clauses

Contract Net Protocol. Contract Net Protocol is a task-sharing protocol defined by Xxxxx and Xxxxx [19] for decentralized task allocation based on calls for bids by a manager and submissions of proposals by the contractors. Many extensions and variations to the Contract Net Protocol have been proposed. In this work we use the one proposed by Xxxxxx et al. [1]. This extension was intended to enable an agent to manage several negotiation processes in parallel, and to reduce the contractors’ decommitment situations. The extended communication primitives used by the managers and the contractors are: Announce, i.e., an agent proposes the execution of a task. PreBid, i.e., an agent makes a temporary bid for the execution of a task. PreAccept, i.e., an agent is temporarily accepted for the execution of a task. PreReject, i.e., an agent is temporarily rejected for the execution of a task. DefinitiveBid, i.e., an agent makes a final bid for the execution of a task. DefinitiveAccept, i.e., an agent is definitively accepted for the execution of a task. DefinitiveReject, i.e., an agent is definitively rejected for the execution of a task. We find Xxxxxx et al. [1] extension very suitable to our problem, since an agent needs to reason about the potential coalitions and collective actions before committing to participate. Once a FRD is decomposed, the avatar sends, as illustrated in Figure 3, Announce messages to all other avatars in its vicinity requesting the execution of all the sub-tasks and actions derived from the decomposition. When another avatar receives the Announce message, it will respond to this request by sending a PreBid message for each of the sub-tasks or actions that it can perform. After a given timeout, the manager evaluates the proposals submitted by the bidders, and selects the best k + 1 prebids for each requested sub-task or action. A coalition is viewed as k-robust [16] (for a given non-negative integer k) if removing any k agents from it leads to a remaining team which can still accomplish the given tasks. Then, the contractor avatar will send PreAccept messages to the best k + 1 bidders for each requested sub-task or action. The coalition is not formed yet since, agents neither know their teammates nor their proposed sub-tasks (or actions). After sending pre-accepts, the manager will set up a constraint network such that each constraint involves bidders from distinct systems. For a FRD, many agents are likely to be proposing a similar atomic service (e.g., in Fig. 2...