| There are more and more web services appearing nowadays and many of them are similar by function. As a result, issues like how to choose the exact ones from the large amount, and how to ensure the correctness of the compositions become one of the most studied aspects of web services. Among these resarches,the most important problem is to provide a proper methord for characterize web services and study their properties, for example, similarity checking and correctness verification. A lot of description languages have been introduced; however most of them are informal. In order to find a more precise approach, we provide a theoretical model for web services and their compositions using formal methods. Based on that, we discuss their similarity properties. The main work of this paper is as follows.Firstly, a new system SVCCS is created on the basic of value-passing CCS, which can describe not only the communication between processes, but also their structural characters. Then, the definition of bisimulation is intrduced for the research of processes equivalence. In order to give a compact descrpition of web services and reduce the complexity of calculating the equivalence of processes, a system named'S-system'is constructed, which is the symbolic system of SVCCS. And, the equivalence of bisimulation between S-system and SVCCS is also proved.Secondly, a formal model of web services named SMWS is proposed, which is based on S-system. On the one hand, SMWS can describe the essential elements of web services, including input,output,precondition and effect. On the other hand, SMWS provides a way to calculate the equivalence of processes by the definition of bisimulation.Lastly, a web services-using framework based of SMWS is proposed. And, the dissertation introduces an algorithm based of SMWS, which can estimate whether two web services are similar or not, by this algorithm, we can validate the similarity between web services and also the correction of the composition of web services. |
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