A Formal Model of QoS-Aware Web Service Orchestration Engine

QoS-aware applications can satisfy not only the functional requirements of the customers, but also the QoS requirements. QoS-aware Web service orchestration translates the QoS requirements of the customers into those of its component Web services. In a system viewpoint, we discuss issues on QoS-aware Web service orchestration and design a typical QoS-aware Web service orchestration engine called QoS-WSOE. More importantly, we establish a formal model of QoS-WSOE based on actor systems theory. Within the formal model, we use a three-layered pyramidal structure to capture the requirements of the customers with a concept named QoS-aware WSO service, characteristics of QoS-WSOE with a concept named QoS-aware WSO system, and structures and behaviors of QoS-WSOE with a concept named QoS-aware WSO behavior. Conclusions showing that a system with QoS-aware WSO behavior is a QoS-aware WSO system and further can provide QoS-aware WSO Service are drawn.