Optimal Adaptation in Web Processes with Coordination Constraints

Contents

We present methods for optimally adapting Web processes to exogenous events while preserving inter-service constraints that necessitate coordination. For example, in a supply chain process, orders placed by a manufacturer may get delayed in arriving. In response to this event, the manufacturer has the choice of either waiting out the delay or changing the supplier. Additionally, there may be compatibility constraints between the different orders, thereby introducing the problem of coordination between them if the manufacturer chooses to change the suppliers. We adopt the paradigm that an abstract Web process flow is pre-specified, and service managers are tasked with interacting with the actual Web services. We focus on the decision making models of the managers who must adapt to external events while satisfying the coordination constraints. We use Markov decision processes as the underlying models for the managers, and show how they can be formulated offline resulting in policies that guide the managers' actions. Our methods range from being centralized and globally optimal in their adaptation but not scalable, to decentralized that is suboptimal but scalable to multiple managers. We also develop a hybrid approach that improves on the performance of the decentralized approach with a minimal loss of scalability.