A Policy-based Adaptation Method for Service Composition

Service composition allows distributed application, for example multimedia application, to be composed from atomic service unit based on the abstract service graph and to dynamically adapt to user´s dynamic service requirements and environment conditions in pervasive computing system. According to our proposed multidimensional QoS model of pervasive computing system, a hierarchy policy model is put forward to capture higher level goals of users, applications, environment and resources and then form rational service composition and adaptation action. Then, service adaptation evaluation algorithm is proposed to maximize a new evaluation criterion - quality of satisfaction of users and environment in order to optimize the optional service selection. Discussion about evaluation algorithm shows that the schema is effective in supporting user and service mobility