Web Services Composition Techniques Based On Workflow And Controllable QoS

Service workflow is an important solution to make service resources workcollaboratively in the distributed environment, and often relies on compositingservices with optimal QoS which are selected from the group of candidateservices. In collaborative manufacturing field, few candidate services have similarfunction so that the scale of candidate services group is not large. Under thiscondition, the traditional method based on selection and replacement of QoS-based nolonger continues to improve the performance of the system.With the purpose of sustainable improvement the whole performance of theservice workflow, the controllability of QoS and service composition frameworksupporting it are studied after the business factors which have an effect on quality ofservice are analyzed. According to above research, the service composition techniquebased on the controllable QoS is studied from space and time sequence. Some specificcontributions of our work are listed as follows:（1）The service workflow composition framework supporting the controllabilityof QoS is proposed. Based on some features of the service workflow, the currentlycommon property of quality of service is studied, as well as the controllability of QoS.According to above research, the service workflow composition frameworksupporting the controllability of QoS is discussed.（2）From the space composition, how to composite service based on variablegranularity is studied. Through analyzing the relationship between the controllabilityof QoS and different granularity service composition which has an impact on QoS,firstly the way to identify business frequency based on service workflow, as well asthe method how to composite web service under these researches is proposed. Finally,under the comparative experiment analysis, the performance can be improved by theservice composition of the multi-granularity and controllable QoS.（3）From the time sequence composition, the research about the qualitycontrollable method oriented service workflow is made. Through analyzing theimportant factors of controllable QoS, the calculation model about prefetching serviceis proposed firstly. It’s proved that this method is more effective than the othermethods of dynamic service prefetching on controlling QoS.In this paper, the service composition techniques based on workflow and thecontrollable QoS are studied. Based on business factors, QoS metrics is extractedfrom the historical operating data. When the system is running, services which are about to be composited are calculated by their adjustment to control the quality ofservice. It’s more suitable for continuing to improve the whole performance of theservice workflow under a small candidate service group.