Research On Several Relevant Problem In Web Service Composition

In the literature of Service-Objected-Computing (SOC), service has been a primary element in Web application. As the widespread use of Web technology and Internet, on one hand, they facilitate clients'access to Web Service; on the other hand, it not only becomes more flexible for the cooperation between one company and another, but also enables each company to provide more complicated value-added products and service via combining the company's service of different kinds. However, how to coordinate and combine between service are confronted with a lot of issues and challenges at the same time, which highlight such questions as compos-ability, synchronism capacity, coordination capacity, correctness checking of Service, and so on. Motivated by these, many researchers have been devoted to try to overcome the above difficulties, as a result, quite a few preliminary progresses in this field have been made, which means plenty of extensive and comprehensive researches are still needed in this field. So, Web service has been, and will still be a extremely hot topic in the future between the academic and industry community due to its vast applied values and its inherent difficulty. This paper is intended to solve several critical problems plaguing the Web service community, our main contribution are as follows:1) On basis of analyzing and exploring the Web service description language extensively and comprehensively, firstly, we bring forward several strategies to describe service dynamic behavior by extending static WSDL, and meanwhile, bring forward the corresponding converted algorithm from extended WSDL language to TLA language, consequently, TLA language can be used to formulate and normalize service.2) Based on the Finite State Automata (FSA) model of service, we make combinations between services, and by assembling and converting the TLA norm of every service via different means of combination, the TLA norm used to describe the process of service combination can be obtained, and furthermore, the corresponding combination algorithm has been put forth.3)With respect to the above combination norm, we traverse the whole model using TLC model checker, to check whether the norm is right or not, and to substantiate the security, correctness, activity and so on, of the combination system. 4) We explore the converted algorithm from BPEL4WS to TLA firstly, and then develop a tool, which can convert from BPE14WS to TLA automatically, on basis of such algorithm.5) The preference of each user is represented by qualitative method, and then a reasoning algorithm, under the condition that there are multiple users with their preference incomplete, is provided. And furthermore, the addressing strategy and corresponding algorithm when there are conflicts among the sequences of users'preference are also proposed.6) By extending the Rank mechanism proposed by F. Rossi, we bring forward a Subrank mechanism. In addition, an example is given for the purpose of showing how the above method can be applied in choosing service in real world.