Submission to ProSim 2000 Workshop Hybrid Simulation Modelling of the Software Process

The paper proposes the combination of three traditional modelling methods (analytical, continuous and discrete-event) into a unique hybrid two-level modelling approach to address software process simulation modelling issues. At the higher abstraction level, the process is modelled by a discrete-event queuing network, which represents the component activities (i.e. service stations), their interactions, and the exchanged artifacts. At the lower abstraction level, the analytical and continuous methods are used to describe the implementation details of the introduced activities. The hybrid approach is applied to a waterfall-based software process to study the effects of requirements instability on various process quality attributes, as effort, delivery time, productivity, rework percentage, and product quality. Simulation results show that the use of the model can provide both qualitative and quantitative suggestions on how to improve the software process or to satisfy specific organisational needs. 1