A qos-aware fault tolerant middleware for dependable service composition

Based on the framework of service-oriented architecture (SOA), complex distributed systems can be dynamically and automatically composed by integrating distributed Web ser-vices provided by different organizations, making depend-ability of the distributed SOA systems a big challenge. In this paper, we propose a QoS-aware fault tolerant middle-ware to attack this critical problem. Our middleware in-cludes a user-collaborated QoS model, various fault toler-ance strategies, and a context-aware algorithm in determin-ing optimal fault tolerance strategy for both stateless and stateful Web services. The benefits of the proposed mid-dleware are demonstrated by experiments, and the perfor-mance of the optimal fault tolerance strategy selection al-gorithm is investigated extensively. As illustrated by the ex-perimental results, fault tolerance for the distributed SOA systems can be efficient, effective and optimized by the pro-posed middleware. 1