The Web Services Composition Using MDP And DT-Golog

If no single Web service can satisfy the functionality required by the user, there would be a possibility to combine existing services together in order to fulfill the request. This trend has triggered Web services composition. The network technology is developing rapidly and the process of global economic integration is accelerating, which make both the internal and external situations of enterprise change enormously. And an increasing amount of companies and organizations only implement their core business and outsource other application services over Internet. Thus, the ability to efficiently and effectively select and integrate inter-organizational and heterogeneous service on the Web at runtime is important step towards the development of the Web service applications.Classical planning suffers from the paradox of first assuming deterministic behavior of Web service, then requiring the additional overhead of execution monitoring to recover from unexpected behavior of services. The inherent stochastic nature of Web service has two points: the non-deterministic of the business logic and the non-deterministic of the quality of service. Markov Decision Process can handle the non-deterministic. Up to the present, many researchers brought forward many methods to solve the non-deterministic. But few ones come down to the logic programming language, such as Golog and DT-Golog, and the planning; also few ones handle the two points of the non-deterministic in a module at the same time.DT-Golog, for Decision-Theoretic-Golog, is a decision-theoretic extension of Golog, which seamlessly integrates of explicit agent programming with decision-theoretic planning. And DT-Golog inherits the feature of the Golog that combining the advantages of programming and planning. This paper aims at the non-deterministics of the Web service in the Web services composition and then establishes the model of Web services composition problems using DT-Golog. The author represents the logic constraints relationship of the Web services with the logic programming using DT-Golog. DT-Golog' interpreter obtains the optimal policy by planning under the constraints which represent the reachable state space of the Web services composition.Finally, the author illustrates Web services composition in the supply chain domain using DT-Golog on the ECLiPSe platform (one kind of developing tool), and the results prove that DT-Golog can handle the non-deterministics usefully.