Research On Compensation Of WEB Service Composition Based On Relational Graph

With the development of Server Oriented Computing and Server Oriented Architecture,the application of web service technology is more and more widely. And because of the growing complexity of the users’ requirements,a single web service cannot meet requirements of users, so it is necessary to composite more than single web service. web service is stochastic, and the Internet environment is heterogeneous and distributed, so the exception of web service composition has become more and more common,resulting in the inconsistency of business process. How to solve the common problems has become a hot topic and make many Experts and scholars to find the solution. Compensation method is used very extensively. Comparing with the roll-back method, it doesn’t need to go back to the start point.Comparing with the replace method, it saves investment, because the compensation services are bound before. The concept of compensation was specified to the transactions of data base system at the earliest. From the point of transaction, it executes the anti-operation for the exceptions to cancel the effect of the exceptions to data base system.This paper studies the solution of exception of web service composition in the context that the sequence of all web services in business process is determined, and every web service can be compensated. This paper uses compensation method to solve the inconsistency of problem.Because of the characters of web services, exceptions are easy to happen. For this problem,this paper puts forward a frame system which is described by relational graph. In this frame system, it needs to do two steps:1. The selection of composition service for each operation in business process: it analyzes every operation in business process, and web service which needs to be invoked .This paper chooses multiple dimensions as the evaluation criterion to decide whether the compensation services meet requirements.Then it uses genetic algorithm appropriately to search and find compensation services, and chooses the best one which has the minimum QoS as the compensation service, and bind it to the operation.2. For the relational graph: it analyzes every operation in business process, and their direct and indirect logical dependency, and confirm their input and output within each other.Then the rational graph of all business process can be structured according to the logical relationship.In this frame system, when the exception happens in business process, it needs to find the location of this exception. By analyzing the record of each operation which has been executed in this business process and the graph, it compensates the operations which need to be compensated, and then invokes their compensation services which are bound before. By experiment, it can verify the feasibility and practicability of this frame system.