【作者】 吴江霞；

【导师】 杨放春；

【作者基本信息】 北京邮电大学 ， 计算机应用技术， 2008， 博士

【摘要】 Web服务组合技术将Web服务视为基本元素,根据应用的需求,将Web服务连接成功能更加复杂的Web组合服务。在功能驱动的Web服务组合中,代表非功能属性的QoS与功能属性同样重要,因为不满足QoS需求的服务组合与不能满足功能需求的服务组合一样无法提供用户期望的服务。判断基于功能需求生成的Web组合服务是否满足QoS需求,以及从功能相似的Web组合服务中选择QoS属性较优的提供给用户十分必要。而这些都需要在Web组合服务执行前对该组合服务的执行期QoS属性进行预测,预测结果作为判断和择优的标准。目前对于Web服务组合QoS预测的研究正处于起步阶段,现有的研究成果相当匮乏。本论文从提高预测方法可行性和准确度的方面对Web服务组合的QoS预测问题进行了探索性研究,主要的创新工作包括以下几个方面:(1)根据Web组合服务QoS属性预测对QoS属性定义的要求,提出了适用于Web服务组合QoS预测问题研究的,基于QoS维度类的Web服务QoS属性定义结构。为服务组合QoS预测问题研究提供了统一的,多方面,多视点的QoS属性类型定义结构,很好地支持了Web服务QoS属性的可扩展特性。(2)提出了一种改进的组合服务流程工作流模型,并基于此模型提出了一种新的Web组合服务QoS属性预测算法。给出了方法的数学语言定义,与现有方法相比本文所提出模型具有更高的抽象层次,支持更多的QoS属性类型,预测数值结果更加全面。(3)采用模型驱动的思想,提出了一种适用于各种Web服务组合语言执行期QoS属性预测的预测体系结构。并基于此预测体系结构,提出了具有良好可行性和较高预测准确度的BPEL业务流程执行期QoS属性预测方法。(4)提出了一种支持事务机制的Web组合服务QoS属性预测方法。分析了Web服务事务机制及其与Web服务执行流程的关系,给出了根据事务异常处理机制估计组合服务可能执行流程的方法,以及根据执行流程估计结果计算组合服务QoS属性值的预测算法。方法具有良好的可行性和较高的预测准确度。更多还原

【Abstract】 Web Service Composition (WSC) takes Web services as basic elements and aggregates them to Web Composite Services (WCS) with more complex functions according to the application requirements. Although WSC is driven by function, QoS is equally important to function, as neither WCS with unsatisfying function nor with unsatisfying QoS can meet the users’ requirements. So it is very necessary to judge whether WCS designed according to function requirements meet the QoS requirements, and to choose WCS with better QoS from those with familiar functions. And this is based on the QoS prediction of WCS before the WCS execution, and the prediction will be taken as the standard of judgment and selection. Now the research on QoS prediction of WCS is in its infant, and the research result is limited. The paper concentrates on the improvement of feasibility and accuracy of the approach on QoS prediction of WCS, and the main innovations are as follows:(1) An architecture for QoS definition is proposed, and the architecture can meet the requirements of QoS prediction of WCS on QoS definition and suitable for the prediction research. The architecture is based on the QoS Dimension Class, and provides general and multi aspects and multi perspective QoS definition structure for QoS prediction, and support the expansibility of QoS attributes of Web Services.(2) A workflow model for WCS process is proposed, and a novel QoS prediction algorithm is proposed based on the model. The approach is defined with mathematic language, and has higher level of abstraction to the approach in existence. The approach can support more QoS attributes and the prediction result is more comprehensive. (3) A model-driven architecture for QoS prediction of WSC languages is proposed, and the approach for QoS prediction of BPEL processes is proposed based on the architecture. The approach has good feasibility and accuracy.(4) An approach for QoS prediction of WCS with transactions is proposed. We analyze the relationship between Web transactions and WCS execution processes, and provide the method to estimate the execution processes of WCS according to the exception handler policies of the transactions in the WCS. And the QoS prediction algorithm is proposed based on the execution processes estimation. And the approach has good feasibility and accuracy.更多还原