Abstract
The Web Services Agreement specification defines a normative language to formulate Service Level Agreements and a basic protocol to expose service-level descriptions, validate service-level requests, and come to an agreement. This protocol, often called “take-it-or-leave-it”, allows a service provider and a service consumer to decide whether to accept or reject a service offer. Although this approach is sufficient for a number of use cases, others exist with requirements for multi-step negotiation or the adaptation of an existing agreement. In this paper, we describe the Web Services Agreement Negotiation protocol, a proposal by the Open Grid Forum to extend the existing specification. This proposal is the result of combining various research activities that have been conducted to define protocols for negotiating service levels or to supersede the existing “take-it-or-leave-it” protocol. The main characteristics of this proposal are the multi-round negotiation capability, renegotiation capability, and compliance with the original specification.