6Framework for Web Service Query Algebra and Optimization

We present a query algebra that supports optimized access of Web services through service-oriented queries. The service query algebra is defined based on a formal service model that provides a high-level abstraction of Web services across an application domain. The algebra defines a set of algebraic operators. Algebraic service queries can be formulated using these operators. This allows users to query their desired services based on both functionality and quality. We provide the implementation of each algebraic operator. This enables the generation of Service Execution Plans (SEPs) that can be used by users to directly access services. We present an optimization algorithm by extending the Dynamic Programming (DP) approach to efficiently select the SEPs with the best user-desired quality. The experimental study validates the proposed algorithm by demonstrating significant performance improvement compared with the traditional DP approach