考虑不确定QoS值的Web服务选择方法

Web Service Selection with Uncertain QoS

随着Web服务的广泛应用,大量功能相似但Qo S(Quality of Service)不同的Web服务部署在Internet上.如何选择满足用户功能和Qo S需求的服务成为了服务计算领域亟待解决的问题.由于受到网络状态、负荷等因素的影响,Web服务的Qo S常常是动态变化的.已有基于Qo S的Web服务选择方法大多假设服务的Qo S是确定的,没有充分考虑到Qo S的动态变化特性,因此在实际中应用可能并不能选择令人满意的服务.提出一种支持不确定Qo S值的Web服务选择方法.该方法采用区间值描述服务的Qo S,先对服务的Qo S区间和用户Qo S需求进行归一化;再通过分析它们之间的关系,建立单个服务Qo S区间效益值的计算模型;最后建立服务的综合效益值计算模型,得到服务的综合Qo S评价.实验表明本文提出的服务选择方法能够很好地适应Qo S值不确定的情况,在选择满足用户Qo S需求的服务方面是可行和有效的.

With the increasing popularity of Web services,more and more services are deployed on the Internet,and many of them are with similar functional properties and different Qo S（ quality of service）. Howto select services with both preferable functionalities and desirable Qo S becomes a challenge in service computing. Because of the significant influence caused by network conditions and workloads,Web services’ Qo S usually changes dynamically. Existing Web service selection approaches,however,usually assumed that Qo S of Web services is certain and did not recognize its dynamic change nature. Thus,they may cannot be applied to practical applications.To address this issue,this paper proposes a method for selecting Web services based on uncertain Qo S,which uses intervals to describe Qo S values of services. Firstly,the method normalizes the Qo S intervals of services and the user’s Qo S requirement. Then,it introduces a model to compute the utility of a single Qo S interval via analyze the relationship between it and the user’s Qo S requirement. Finally,it employs a function to compute the comprehensive utility of Web services’ Qo S,and ranks all Web service candidates for the user.Experimental results demonstrate that the proposed approach is feasible and effective in selecting satisfactory services for users.