| Nowadays, many research institutions have conducted several researches on all aspects ofWeb services composition at home and abroad, and some achievements have been made. ButWeb services composition is a new subject with continuous development, so there are a lot ofissues in the progress of exploring, practicing and using. The research on Web servicescomposition is always progressive. Some issues have been studied by a lot of researchers; theyhave put forward their points of view. For example, the description of Web services in the Webservices composition, and the selection of models, and the selection of the Web services aboutQOS, and how to test in order to make the Web service correct, and the fault diagnosis whenthe problems appear.In this paper, the solutions for services composition are discussed in theory and in thenatural characters of the issues. We discuss and study several critical issues of the Web servicescomposition, in other words, we assimilate the useful points from the research achievement past,and we improve the services in the aspects of the issues appeared. Through exploring severalcritical and key issues in the Web services composition, we make the methods of the Webservices composition improve, make the running progress more correct and make the use in eachaspects of society wider. The value and function can be incarnated. The main works by theauthor include the following aspects:1 We make a brief introduction and describe to the single Web service and why we need touse the Web services composition first.2 We make an introduction to several services composition methods and the characters ofeach model. For example, the Web services composition method based on workflow, the Webservices composition method based on Artificial Intelligence (AI), the Web services compositionmethod based on Petrinets, the Web services composition method based on Process Algebra.We compare several models of the Web services composition on the aspects of connectivity,non-functional requirement, correctness and reliability. The model of Pi calculus has been usedto describe the Web services composition.3 The selection of Web services is a difficult and key issue in the Web services composition.We want to find the services which can fit on the users’requests, ensure the reliability，and thecreditworthiness ,but the cost and the time is the least, How to select this kind of services is thedifficulty. We bring in the concept of QOS, and use the QOS to select the services .In the serviceselection algorithms based on QOS, we define the computational model of QOS which can be used to select Web services. Then we use the Travel Agent System which is the classical modelin the Web services composition to describe specifically.4 After the structure of Web services composition, we need to test the characters of thecomposition such as: correctness, replaceability and compatibility in order to ensure the Webservices composition run correctly and fit on the dynamical Internet environment and thedeveloPing requests from the users. In this paper, we describe the three characters of Webservices composition and use the method of Pi calculus to test.5 As a composition service, the fault diagnosis and renovation are very important. Thepoints in the Bayesian network show the direct causal relationship, and this kind of causalrelationship is uncertain. So we can deal some uncertain issues with the Bayesian network. Wepropose a fault diagnosis algorithm based on Bayesian network because of the characters of theBayesian network.In summary, we present some key issues of Web services composition, explain some baseConcept formula, describe the background of the issues and the research achievements at homeand abroad, analyze the issues and summarize the solutions. We use some diagrams to describesome abstract issues in order to understand and solve the problems better. Which we have studiedwill have certain significance to the developments and applications of Web services composition. |
PDF Full Text Request