Researching Service Substitution In Composite WEB Service Based On QoS

With the service-oriented architecture (SOA)’s mature and promotable,web service composition technology provides a highly interoperable, cross-platform and loosely coupled new way of communicating and collaborating the small-grained web services to achieve large-grained services.However, due to the network’s openness and complexity,web service exists in a state of great uncertainty, and therefore the issue of credibility of web services has obtained widespread concern.How to ensure the credibility of composite services?On the one hand you need to select the credible web services to compose.On the other hand, composite services need to have strong error recovery capability.The two tips above are to ensure the composite services’ effective during the execution.This paper is concerning about how to improve the credibility of composite services from web services substitution when some service failed.Through analyzing service substitution’s theory and technology of web services in recent years,this paper has put forward a services substitution method which is based on the Quality of Service (QoS).First, analyze the substitutability of failure service in a composite web services environment,which has improved the selectivity of candidate alternative services and made the service substitution diversification.This paper also has put forward the service clustering model CMFSS which is based on the service substitution.This model classifies the services according to functional classification and describes the services’relationship between input and output parameters.The main role of the CMFSS is to find alternative services combined with automatic service composition technology.Based on the analyzing and modeling of the service substitution, finally,this paper has put forward the service substitution method which is based on QoS.This method, which combines with single-service substitution and service subgraph substitution, select substitution services according to consider local QoS constraints first then the global QoS constraint, and finally get the new composite web service to meet the requirements.Simulation experimental results show that, compared with the traditional service substitution method, the service substitution method which the paper presents can improve the selection range of alternative services more effectively, and under the premise of guaranteeing the quality of composite service’s QoS, it can improve the success rate of the service substitution.