Port Based Reliability Computing for Service Composition

Web service composition is a distributed model to construct new web service on top of existing primitive or other composite web services. However, current service technologies, including proposed composition languages, do not address the reliability of web service composition. Thus it is hard to predict the system reliability. In this paper, we propose a method to compute system reliability based on Service Component Architecture(SCA), a standard that provides a language-independent way to define and compose service components in the system. We first present a formal service component signature model with respect to the specification of the SCA assembly model, and then propose a language-independent dynamic behavior model for specifying the interface behavior of the service component by port activities. Then the failure behaviors of ports are defined through the Enhanced Non-Homogeneous Poisson Process(ENHPP). Based on the semantics of ports, several rules have been generated to compute reliabilities of port expressions, thus the overall system reliability can be automatically computed. Finally, a testing bed is given to calculate port reliability.