Research On Exception Handling Mechanism Based On Directed Graph In Service Composition

With the application of Web service composition more widely, in the process of service composition problems have give increasingly prominence in the implementation of Web service composition, so the exception has become a the most common problem of service composition, but also a hot topic。In order to implement consistency and reliability of composite services implementation under the Web services circumstance, exception handling has become an essential part that it can guarantee for the consistency and integrity of Web service composition, then the exception handling method as an effective means that it get the attention of many researchers. In exception handling, through compensation method eliminate affection of the finished service, which achieve has been to achieve composite service execution forward or backward recovery, the key issue is to ensure consistency.Exception handling mechanism is essentially to achieve a consistent state of the overall business process, by the use of exception handling method. This paper aims at in-depth study for the process of exception handling, and combines with the traditional exception handling methods, this paper proposes exception handling mechanism based on directed graph in Web service composition. While this paper focus on this exception handling mechanism doing the following work:1. Research on the traditional exception handling mechanisms. Which mainly include the failure of compensation method, base Agent approach, modeling method, multiple exception handling strategy method, etc, through analyze the traditional method of exception handling and combine the characteristic of Web service composition, summed up exception handling method in the business process.2. This paper proposes an exception handling mechanism of based on directed graph in Web service composition. While analyzes the feasibility of this exception handling mechanism and the main process of the achievement, the first, a directed graph method used to establish logic function model, followed by business process based on the implementation dependencies between tasks generate compensation dependency directed graph, and finally when business process exception occurs, the risk of compensation by the value judgments to select exception handling approach. This approach, while ensuring the implementation of compensation, taking into account compensation for services or compensation does not exist the problem of high service cost. Then the algorithm obtained through the algorithm comparing the advantages.3. Analyzed based on directed graph exception handling in Web service composition, exception handling will encounter some problems. Depth analysis of the problem by one by one, each is given to solve these problems. And finally through the simulation experimentation show that, when the Web service composition in the abnormal, the method when an exception occurs to ensure the reliability of composite service execution and consistency.