摘要
WS-CDL是一种主流的Web服务组合标准,描述了基于编排机制的端对端服务组件的组合方式。对基于WS-CDL的服务组合进行可靠性预测,能帮助Web服务的使用和管理者定量考察服务的可信性,并帮助他们从功能相同的服务组件中择优选取以优化整体服务流程的可靠性。然而,学术界对WS-CDL可靠性研究非常匮乏。提出了一种模型驱动的方法来预测基于WS-CDL的组合服务的可靠性。该方法首先引入一系列的转换规则,将WS-CDL中的各种活动和结构转换为等效的NMSPN网描述。在生成的NMSPN网基础上,引入了一个预测算法以分析组合服务的"流程正常结束概率"。为了对理论模型和结果进行检验,还通过WS-CDL+执行引擎对服务组合的实例进行执行并获得了流程正常结束率的实验数据。比较发现,由实验数据导出的95%置信区间完好地覆盖了理论分析结果,表明了该方法的正确性和精确性。
Web Services Choreography Description Language（WS-CDL） is a main-stream standard for the description of peer-to-peer collaborations for the participants for service composition.The dependability of composite service processes specified in WS-CDL is predicted.It allows service designers and uses to decide whether the process meets the non-function requirements of trustworthiness,and to choose the process with better dependability from those with identical function.But, very limited research attention is paid to dependability of WS-CDL.This paper proposes a model-driven approach for dependability prediction of composite service based on WS-CDL.To model a composite service in a quantitative manner,a set of translation rules is given to map WS-CDL elements into Non-Markovian-Stochastic-Petri-Nets（NMSPN）.Based on the NMSPN representation,the prediction algorithm is introduced to calculate the process-normal-completion-probability as the metric of dependability of service composition.The accuracy of the approach in the experimental study is also validated by showing 95% confidence intervals obtained from experimental dependability results cover corresponding theoretical prediction values.
出处
《计算机工程与应用》
CSCD
北大核心
2011年第11期60-66,101,共8页
Computer Engineering and Applications
