Quantitative analysis of MTTF of composite web services

Although the reliability of the composition of web services (WS) has attracted much research work, an important facet of it-meantime to failure (MTTF) has not been given enough consideration. The research presented in this paper intends to fill this gap by illustrating on an example of composite WS how the redundant system works and what kinds of practical results can be derived. The main contributions of this work are as follows: First, we provide the concept of MTTF of composite WS, which has drawn little concern in previous work. Second, the calculation method of MTTF of composite WSs is described based on the workflow composition pattern. Third, we present the quantitative analysis of MTTF of composite WS for non-redundant services, part-redundant services, and all-redundant services-based systems. And we show, by an experiment, that to achieve the higher reliability of a system, it is necessary to decrease the failure rate and increase the repair rate in addition to providing a redundant system.