Research On Agent-Based Web Service Composition Technology

With the development of the technology and the specifications of web services, the concept of web service has been widely accepted by people. At the same time, more and more business enterprises will distribute their services in the form of web services so as to gain more and more profits. Combining many services into a system to realize more complicated functionality is the common application of web services nowadays. In an environment of web services, when the web services become available, composing web services will provide enterprises with the probability of enhancing web services' value.The dissertation aims to study several pivotal technologies in the web service composition. The current technology of service composition under the Internet has two limits: one is the lack of the autonomy, adaptability and individuation of web services. The other is the limit of the network adaptability and the monotony of the interaction of web services. Software agent technology is an active researching area in the current software technology. The software agent is characterized by the following properties: autonomy, social ability, intelligence, etc. And now, it is a technical basis of the new generation software middleware platform. Based on the above-mentioned problems, several pivotal technologies in the web service composition are discussed and a web service composition framework is proposed. Following efforts are presented in this dissertation:(1) The expansion of web service description modelThe general description of web service is WSDL (web service description language), and the performance of service is an important aspect of service measurement. In order to describe a service more detailedly so as to select services dynamically at the runtime, an expanded description model of web service is proposed by adding the specification of the quality of services. The value computation methods of the price, execution time, reliability and the availability are listed and a service discovery mechanism is introduced.(2) The selection of services in the compositionBased on the above quality model of service, a local optimization selection algorithm is introduced. Then, a mathematical model of a global planning selection algorithm is given, and its solving method is discussed. Two algorithms are all designed from theperspective of service composition.(3) The design of service composition frameworkA service composition framework based on the agent technology is presented. The design idea, the structure of the framework and its elements as well as the relationship of them are all discussed in detail. Finally, the execution flow of the framework is introduced.(4) The development of the service composition platformA part implementation of the above framework is presented. With an instance, the composition flow and the execution mechanism which is implemented by a multi-agent system are emphasized.