| At present,the Service composition has been a popular research.Its approach can be classified into manual composition,semi-auto composition,and automatic composition.Locating a composite service would require accurate specifications of both service descriptions and user requests.Constraints are used to be located.They are of two types:local and global constrains.Global comstrains can be classified into strictly dependent constrains and independent constrains.This article uses the semiautomatic method in view of the independent global constrain's Web service composition to conduct the research. The independent global constrain is that for a global constrain,if an attribute is evaluated,the left limited attribute value can not be only determined.If a given independent global constraint restricts q attributes,and if service description assign p values to each attribute,then a technique locating a conforming service may have to consider pq combinations of values,so independent global constrain for Web service composition is a difficult problem.The semiautomatic method is that the exploiter constructs an process model first, and then it automatically selects the module for each abstract task. This article first introduces the Web service, the composition related conception and the research's present situation, then introduces the fuzzy Petri net and the constrain related knowledge, and then discussed different situations between two global constrain fuzzy Petri nets'composition.Afterward this article uses the fuzzy Petri net to carry on the modeling to the independent global constrain-aware Web service composition, and has given a Niche Genetic algorithm, with which the most superior composition was found in the model.Through the simulation experiment, we might see that this method not only save the time but have the high ratio of feasible solution.It also proposes correctness and the reliable proof technique under the constrain-aware Web service composition in last part of the article. Correctness is to confirm the constrain satisfied situation and to have the service function corrected.The reliability is the guarantee of service quality under the consideration of constrain situation,through transforming the single service's reliability into transition reliability in the fuzzy net model under the dependent relationship, gives out the token value computational method in the place when the composition service is conducted. Then it constructs service composition's reliable confirmation chart and explains the service composition through the reliability of this confirmation chart. |
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