Evaluating proposals in web services negotiation

Negotiation is a crucial stage of Web Services interaction lifecycle. By exchanging a sequence of proposals in the negotiation stage, a service provider and a consumer try to establish a formal contract, to specify agreed terms on the service, particularly terms on non-functional aspects. In this paper, we propose an approach for proposal evaluation, one of the key decisions in negotiation that determines the acceptability of a proposal. Fuzzy truth propositions are employed to represent the restrictions attached to a service, and a utility function is used to capture the negotiator's preferences over service attributes. The overall acceptability of the proposal can be determined by the restriction obedience and the utility of values for service attributes, collectively. Based on the acceptability of a proposal, a negotiator can decide whether to accept it as a contract, then enact with the party that offers the proposal.