The Modeling And Analysis Of Web Service Composition Based On Price Time Petri Net

With the economic globalization development, more and more business organizations start their business in the global economic domain. In order to adapt to the dynamic market environment with increasingly fierce competition, many companies begin to build their businesses procedures on the Internet, release their professional work as Web service, and provide them to their partners. Under the strong incitement of the market demand and present condition, Web service has become popular in academic and industrial domain, and has become one of the important methods carrying out the automation of dynamic business process. For enhancing validity of Web services, its QoS is becoming more important. The evaluation standards of QoS mainly including implementation cost, implementation time, reliability and reputation etc.This paper mainly carries on an analytical research on the cost of Web's quality of service. At first, a model of Price Time Petri Net is presented, which is attained by extending price information in Time Petri Net. It is convenient to define Web service composition and the rules of service choreography by using PTPN to describe Web service composition. Making use of the PTPN model, we can give a formal description of the procedure of combination flow, and can also guarantee the accuracy and reliability of service combination by testing various characteristics of Price Time Petri Net such as liveness, reachability, boundedness and so on. Next, using a method of state space computing and the analyze method of adding a price attribute in extended state class on Web service composition based on Price Time Petri Net, this dissertation discusses the reachability of minimum cost. In order to satisfy customers' demand for minimum cost of web's quality of service, an algorithm is quoted here. The minimum cost can be attained by that algorithm. Finally the author gives a Web service composition example, and gets the following conclusions from the analysis of this example's model: Price Time Petri Net is an excellent tool to analyze Web service composition, and it is feasible to study the minimum cost of Web service composition.