A Session-based Interaction model for Cloud Service

Being executed in the Internet space, cloud services provide elastic computing resource to satisfy customers’ demand. Since single service usually can't suit their complex need, customers need to assemble multiple services into one service workflow which coordinates individual service to fulfill the specific task by means of service interaction. Obviously, the interaction mechanism of cloud service is the glue of workflow and plays an important role in service workflow. However, owing to the dynamic characteristic of the Internet, cloud service interaction is complicated and volatile. Hence, the question how to describe and formalize the complex interaction of cloud service workflow is a non-trivial work, which has directly influence on the overall design of cloud service architecture engineering and its performance.

Consider the question above, this article put forward a session-based interaction model of cloud service. Regarding the complexity of service workflow, this paper applies the divide-and-conquer strategy to decompose the interaction of cloud services into session, then constructs the interaction model of cloud service. In the first step, we introduce and formalize the notion of session, so the complex interaction of cloud service workflow can be decomposed into hierarchical session pattern, which is easy to formalize by the guard automata. Next, using the session as the abstract data type, the session-based interaction model is proposed in order to facilitate the formalization of cloud service workflow. In addition, the model incorporates the notion of role and business protocol to strength the model flexibility. Like the role of object in object-oriented programming language, this model provides a new perspective for modelling the cloud service workflow and lay the solid foundation for its formal verification.