A heuristic approach to optimal service selection in service oriented architectures

Service Oriented Architectures (SOA) enable a multitude of service providers (SP) to provide loosely coupled and interoperable services at different Quality of Service (QoS) and cost levels. This paper considers business processes composed of activities that are supported by service providers. The structure of a business process may be expressed by languages such as BPEL and allows for constructs such as sequence, switch, while, flow, and pick. This paper considers the problem of finding the set of service providers that minimizes the total execution time of the business process subject to cost and execution time constraints. The problem is clearly NP-hard. However, the paper presents an optimized algorithm that finds the optimal solution without having to explore the entire solution space. This algorithm can be used to find the optimal solution in problems of moderate size. A heuristic solution is also presented and experimental studies that compare the optimal and heuristic solution show that the average execution time obtained with a heuristic allocation of providers to activities does not exceed 6% of that of the optimal solution.