Research On Key Technologies Of Composition And Exception Handling For Web Service

Recently, web service has been the main way to achieve the application of service-oriented architecture, which makes the web service composition technology become a hot topic for researchers. By combining different Web service resources, it can form a powerful service to meet the user demand. Based on the existing SOA methods, this paper studies four key technologies in the life cycle of web service composition, including optimal web service composition, formal verification model, exception monitoring, and exception handling. To realize optimal web service composition, the strategy by the improved ant colony optimization is presented. The formal verification model of web service composition is proposed based on the fuzzy Petri net. The exception monitoring algorithm is explored by using event calculus to guarantee the quality of service. Finally, the exception handling framework is introduced by means of Bayesian network.This major work includes the following four aspects:1) Proposed an ACO-based approach for optimal web service composition, and the traditional ACO algorithm is improved by modifying state transition probability and pheromone update rules to accelarate search speed.2) Established a formal verification model of web service composition by the fuzzy Petri net. The reachability and the liveness are used to judge whether the web service is true or false, and the accuracy of this formal verification is improved.3) Introduced a runtime monitoring mechanism for web service composition by using event calculus. The behavioral model of web service is build as well as the definition of illegal inconsistent criteria, which can fulfill runtime behavior correctness monitoring.4) Introduced an exception handling framework for web service composition based on Bayesian network and the mapping between web service composition and Bayesian network. According to the priori probability and the conditional probability, the exception diagnosis can be carried out for web service composition. After that, the optimal candidate of web service composition is applied to replace the excetpion services, in order to acheive exception handling.