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This paper proposed a hierarchical service overlay network framework (HSON) based on the analysis of advantages and disadvantages of the present service composition network framework and the characteristics of service composition applications, and studied service composition mechanism based on HSON.. The Petri net is adopted to describe the service composition mechanism, and verify the correctness and completeness. In the end, we used examples to verify the reasonable of using HSON to get service compositon. Introduction Service composition can depend on user demands to put some discrete, existing fine granular basic services into complex corse-grained services with new functions, so as to realize the development and customization of the services. This is a mainstream of development direction of the network service in the future, and will be increasingly extensive applied. There still exist some problems in the current service composition technologies, especially the lack of unification of the research about the key technical problems under the appropriate network architecture, which makes the service composition limited in some specific application fields and the smaller range of network. But with the progress of Internet technology and the continuous development of Service Composition application, to provide users with Service composition which are various fields oriented, wan range and based on QoS guarantee is the future trend of service composition development, so this paper proposes a hierarchical service overlay network framework HSON which is service composition oriented. We also described and validated the Service composition mechanism based on HSON. Hierarchical service overlay network framework HSON Overlay network caused attention and received extensive development because of some characters of itself, such as high flexibility, scalability, easy to implement and deployment new services. Service overlay network frameworks relevant with services currently mainly include two categories. First, it is the overlay network framework which builds on the communication subnet. Among this, service overlay network which represented by paper [1] is built overlay network on the communication subnet, and deploys services gateway between different ISP. Logical connection between two Service Gateway is provided by the bottom layer's ISP and it must satisfy the bandwidth request and service qualities, and the service qualities are defined by a bidirectional SLA. Service overlay network bypasses the connection point between ISP in this way in order to avoid the resultant performance problems and guaranteed the good performance of the end-to-end application which across multiple ISP. There are a lot of researches related to this thought, for example, Paper [2],[3] and [4] studied the problems in the construction process of the overlay network. Paper [5] and [6] studied the topology configuration problems of overlay network. This type of overlay network is mainly to solve the routing problems between different ISP in the service network, but it costs too much in construction. Meanwhile, it can not only deployed on a large 6th International Conference on Machinery, Materials, Environment, Biotechnology and Computer (MMEBC 2016) © 2016. The authors Published by Atlantis Press 2126 number of services in the cover nodes. Therefore, it is not suitable for constructing the service composition network framework. Second, it is P2P network framework. Paper [7] constructed a framework of service composition based on P2P network characteristics including no center, self-organizing and high efficient routing and so on. But considering the problems such as security, easy to manage in the process of service composition, service components generally distributed in the high performance controllable node in the network instead of distributed on the end-to-end system. So it will bring security problems and other issues by using P2P system as network framework of service composition. After we deeply studied the advantages and disadvantages in the current service composition framework, we propose a service composition framework oriented to service composition which called hierarchical overlay network framework(HSON) , as is shown in Fig1. Our basic idea is: first of all, use the autonomous domain as the basic units. Then, collect a large number of available content servers of the network, and construct domain overlay network by the method of deploying several proxy servers of service composition.Next, chose some super nodes in every domain depending on the needs of service composition in inter-domain, and built the network of inter-domains with the super nodes which called core overlay network as well. Finally, establish service index of inter-domain based on the correlation between the services and other factors. Through these three steps, hierarchical overlay network framework (HSON) was created successfully. HSON not only has high efficiency of physical network, but also has the flexibility of overlay network, and can deploy a large number of service components according to the correlation between services, so it can provide users with applications of service composition which can be implemented in a WAN range, and many fields of application. An application of Service composition can occur in an autonomous domain, and we call these services as service composition in domain. An application of Service composition can also take place in many autonomous domains, and we call it service composition in inter-domains. According to the mode of service composition, the structure of service composition can be linear and parallel. This paper using HSON as service composition framework, to study the mechanism of service composition based on HSON. The verification of reasonableness of workflow Model has become an important part of the work flow system, and has played an important role in safe and stable operation of the entire system. Description of service composition mechanism based on HSON We use the examples of response procedure of user request to describe the service composition mechanism based on HSON. To better describe this, we ignored some treatment about anomalies problems such as the service server suddenly crashes when in a service process. We will introduce the procedure of service composition based on HSON Model followed. 1 Users send service requests to local proxy servers of service composition. 2After receiving a request for content, local proxy servers of service composition will find the components which meet the demands of service composition in its own service directory. If all the components are found, local proxy servers of service composition will complete the work of choosing routing way of service composition: First, judge the routing structure of service composition, if it is a linear structure, then excute the algorithm of service routing choosing for linear structure to choose routing; while, if it is a parallel structure, then excute the algorithm of

Petri Net Verification of Service Composition Mechanism based on Hierarchical Service Overlay Network