| Web service composition is a technology that composes multiple Web services withsingle function according to certain logical order and is smooth executed by callingrelationships between services to meet the complex functional requirement. With the rapiddevelopment of the Internet, especially the emergence of cloud computing and mobilecomputing technology, more and more organizations and individuals place their businessin the form of Web service in the Internet or the cloud. These services can not only meettheir own business needs but also provide services to the outsize world. An open Internetapplication environment is formed, and which laid the foundation for the on-demandservice composition. In this environment, there are too many service providers and servicerequestors to meet the needs of the application by manual service composition. Automaticservice composition has become the main trend of the service composition.This paper carries out research for several key issues in automatic servicecomposition. In order to increase the degree of automation of the service composition,optimize the performance of service composition, ensure the correctness of servicecomposition and improve the success rate of service composition, the following studiesare carried out based on semantic Web service.Firstly, in order to improve efficiency of building service dependency graph andidentify the control structure of the logic flow automatically, service dependency graphthat meet input-output request is established quickly based on input set inverted indextable and output set hash table. The flow control structure is identified automatically basedon the semantic matching relationship on service interface. Put semantic matching degreeas the optimization goal, the improved breadth-first search algorithm is designed toachieve optimal path search.Secondly, in order to ensure that the composition function real meets user functionalrequirement, this paper introduces the function ontology to describe the actioncharacteristics of the Web service. And then a hierarchical graph of the function ontologyis built based on the relationship between the function ontology, the function mergence mechanism in function ontology graph is invoked, so that the function correctness of eachcomposition path is verified.Thirdly, in order to achieve Web services multipath global optimization based onQuality of Service(QoS), a path template mechanism is designed to achieve unifiedmultipath fixed-length encoding of genetic algorithm, the path template mechanism isused to control the generation of individuals in the initial population as well as incrossover and mutation, by defining the QoS aggregation formula of multipath choicestructure, the unified multipath fitness function is designed, so that the multipath globaloptimization is realized by a single running. Moreover, in order to fully reflect theuncertainty of quality of service and the ambiguity of user preferences, this paperintroduces the fuzzy sets theory into QoS-based Web services composition, the QoSattributes and user preferences that are not suitable for accurate representation aredescribed by triangular fuzzy number. Then fuzzy multi-objective genetic algorithm isdesigned by rewriting the Pareto dominance relationship, the multipath and multiple QoSglobal optimization is realized.Finally, in order to solve the problem of the message heterogeneous during theexecution of composite service, this paper first analyzes the manifestations of messageheterogeneous, and then a vertical and horizontal mapping mechanism is built based onontology matching, semantics heterogeneous match of message elements is realized. Onthis basis, the syntax heterogeneous solution method is designed based on the the messageinstance testing and service replacement mechanism. The experiment shows that thismethod can effectively improve the execution success rate and reduce the data distortionrate of the composite service. |
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