A formal method to model and analyse QoS-aware fault tolerant service composition

In this paper, we address the fault tolerant service composition with particular attention to QoS. A fault tolerant strategy for improving the performance of service composition is proposed. The strategy is composed of invocation mechanism, synchronisation mechanism and exception mechanism. Petri nets are used to observe the behaviours of basic components, and to describe their interrelationship. The transaction attributes, reliability, and time of service are also articulated. The composition mechanism systematically integrates these schemas into a fault tolerant model. Based on this, the analysis technology and its enforcement method are proposed, which can guarantee the correct behaviour of service composition while meeting the required reliability. The related theories of Petri nets help prove the correctness of the strategy. Finally, the method is realised by a simplified travel service and is tested by several experiments.