Negotiation Protocols. A negotiation protocol defines the set of policies which determine possible interactions among participants [10]. Broadly, the protocols can be classified as bilateral or mul- tilateral, depending on the number of participants. One of the well-known bilateral protocols is described by Xxxxxxxxxxx and Xxxxxxx [145, pp.40-41], the monotonic con- cession protocol. It starts when both negotiating parties submit their proposals at the same time, and if they overlap in terms of the negotiators’ utilities, then an agree- ment is reached. If not, negotiation proceeds to the next round until an agreement is reached or no negotiators have conceded further. The overlapping of proposals in terms of the negotiators’ utilities means that at least one negotiator gains a better utility by accepting an opponent’s proposal than clinging to its own. The other widely implemented bilateral protocol is the alternating offers protocol, pro- posed by Xxxxxxxxxx [154] and then adopted in much other work [9, 17, 25, 112]. This protocol assumes that negotiators exchange proposals in turns, which is different from a monotonic concession protocol. There are different versions of this protocol in respect of the options to reply and conditions to terminate negotiation. In general, the options to reply to the opponent’s proposal for a heuristic-based approach are: (i) accept a proposal; (ii) reject a proposal and quit negotiation; (iii) reject a proposal and send a counter-proposal or a critique [155]. Here, a counter-proposal means a proposal in response to the opponent’s proposal and it generally intends to be more appealing to an opponent than the previous negotiator’s proposal. A critique contains a statement whether and/or why it likes or dislikes the whole or part of the opponent’s proposal. A counter-proposal is much more common in this protocol than a critique as it offers a particular alternative solution rather than just a statement with its preferences. A negotiation process ends when one of the negotiators accepts its opponent’s proposal, quits negotiation or a deadlock of negotiation is reached (e.g. the deadline of negotia- tion). A multilateral protocol is often presented as an auction model e.g., [130,156], or as mul- tiple concurrent bilateral negotiations e.g., [157–159], coordinated by a central mecha- nism. Multilateral protocols may refer not only to a negotiation process with multiple opponents, but also to a negotiation process with multiple issues. For example, ...
