An Automatic Configuration Algorithm for Reliable and Efficient Composite Services

Reusability is a central concept of Web services as it allows for the construction of composite services. Thus, an existing composite service can be combined with other composite services to form more complex nested or hierarchical services. Reliability and efficiency are the main requirements of composite services construction. The reliability requirements are rigorously defined by designers using the accepted termination states concept. The efficiency requirements are tightly related to a set of quality-of-service (QoS) constraints that are required by customers. In this paper, we first developed a hierarchical model for composite services. Based on this model, we developed a recursive procedure for the automatic computation of the transactional reliability and QoS of composite services. Second, we proposed a new concept, called required efficiency level, to offer more flexibility to the customers to specify their needs in terms of QoS. Third, we developed a new composite service configuration (CSC) algorithm for the construction and adaptation of composite services while considering the reliability and efficiency requirements. The originality of the CSC algorithm consists in a new recursive global QoS constraint decomposition procedure. Finally, we conducted a set of experiments to evaluate the benefits of the proposed CSC algorithm in comparison with the related work. These experiments confirm that our CSC algorithm is able to generate, in a timely fashion, reliable, and efficient composite services.