中文摘要：

由于组合应用需求超越了传统事务，为了保证组合服务事务的性质，不可避免地需要合适的失败恢复机制，以提供持续的和可靠的执行语义．提出一种组合事务恢复模型，采用向前、向后和替代恢复的综合事务恢复策略实现失败恢复的动态编程，将失败恢复策略从业务流中分离出来建模．与高级事务聚合模式相对应，任务执行失败将影响组合事务流程的执行进展．然而，现有的QoS性能估算方法并没有考虑失败恢复产生的影响，因此，不能直接用于组合事务的QoS估算．根据事务正确和出错情形，提出了一个基于组合事务的QoS评价和估算模型．实验证明，该模型能有效地估算和分析组合事务性能，对于减少事务失败率和消除不利因素影响有较好的效果．

英文摘要：

To assure its transactional properties, composite Web service based applications require more transactional supports than traditional transactions, which has inevitably led to the need for appropriate failure recovery mechanisms that can provide sustainable and reliable execution semantics. In this paper, a comprehensive transaction recovery model is proposed, which includes forward recovery, backward recovery and alternative recovery. Failure recovery strategies are separated from business flow to dynamically model and program the failure recovery. With respect to the advanced aggregation patterns, since failed task will affect execution proceeding of Web composition transaction, and the existing QoS evaluation methods do not consider failure recovery, it can not be used directly in QoS estimation of Web composition transaction. According to the situations of both correct and failed, a QoS estimation model based on the performance of composition transactions is proposed. The results show that the proposed model can evaluate and analyze the performance of composition transactions effectively, reduce the failure rate of composition transaction, and eliminate the bad effects efficiently.