Local martingale difference approach for service selection with dynamic QoS

AbstractUsers in Service-oriented architecture (SOA) seek the best Quality of service (QoS) by service selection from the candidates responding in succession. In case the QoS changes dynamically, choosing one service and stop the searching is problematic for a service user who makes the choice online. Lack of accurate knowledge of service distribution, the user is unable to make a good decision. The Local Martingale Difference (LMD) approach is developed in this paper to help users to achieve optimal results, in the sense of probability. The stopping time is proved to be bounded to ensure the existence of an optimal solution first. Then, a global estimation over the time horizon is transformed to a local determination based on current martingale difference to make the algorithm feasible. Independent of any predetermined threshold or manual intervention, LMD enables users to stop around the optimal time, based on the information collected during the stochastic process. Verified to be efficient by comparison with three traditional methods, LMD is adaptable in vast applications with dynamic QoS

Web Services and Formal Methods

none3siThe proceedings contain 18 papers. The topics discussed include: service QoS composition at the level of part names; SCC service centered calculus; semantic querying of mathematical Web service descriptions; verified reference implementations WS-security protocols; translating Orc features into Petri Nets and the join calculus; dynamic constraint-based invocation of Web services; a formal of contracts for Web services; execution semantics for service chreographies; analysis and verification of time requirements applied to the Web services composition; a formal approach to service component architecture; evaluating the scalability of a Web service-based distributed e-learning and course management system; chereography conformance analysis: asynchronous communications and information alignment; and towards a unifying theory for Web services composition.noneM. Bravetti; M. Nunez; G. ZavattaroM. Bravetti; M. Nunez; G. Zavattar