QoS modeling and analysis of component-based software systems: a stochastic approach

There is a growing demand for using commercial-off-the-shelf (COTS) software components to facilitate the development of software systems. Among many research topics for component-based software, quality-of-service (QoS) evaluation is yet to be given the importance it deserves. In this paper, we propose a novel analytical model to evaluate the QoS of component-based software systems. We use the component execution graph (CEG) graph model to model the architecture at the process level and the interdependence among components. The CEG graph can explicitly capture sequential, parallel, selective and iterative compositions of components. For QoS estimation, each component in the CEG model is associated with execution rate, failure rate and cost per unit time. Three metrics of the QoS are considered and analytically calculated, namely make-span, reliability and cost. Through a case study, we show that our model is capable of modeling real-world COTS software systems effectively. Also, Monte-Carlo simulation in the case study indicates that analytical results are consistent with simulation and all are covered by 95% confidence intervals. We also present a sensitivity analysis technique to identify QoS bottlenecks. This paper concludes with a comparison with related work. Copyright (C) 2007 John Wiley & Sons, Ltd.