A Policy-Based Middleware for Web Services SLA Negotiation

Negotiation of service level agreements (SLAs) is very important for maintaining quality of service (QoS) of composite Web services-based business processes. The process of negotiation involves specification of negotiation parameters, exchanging offers to conduct the actual negotiation process, and then finally generating the formal SLA if the negotiating parties come to a consensus. We propose a negotiation broker (NB) middleware framework to facilitate automated negotiations of SLAs for Web services in a service oriented architecture (SOA). High level business goals, contexts, preferences, constraints, and values of the negotiation issues are expressed as a policy specification by each of the negotiating parties. The NB maps the policy specifications to low level negotiation strategy models and parameters in order to conduct the negotiation locally as a trusted broker. We present a model and an example of the high level negotiation policy specification. We also present our NB framework including a prototype implementation to illustrate the mapping of the policy to a time-dependent negotiation strategy model.