Hybrid simulation modelling of the software process

Abstract

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 queueing network, which represents the component activities, their interactions, and the exchanged artefacts. At the lower abstraction level, the analytical and continuous methods are used to describe the behaviour 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, such 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 on how to satisfy specific organisational needs. Although, the model has been primarily designed to represent the behaviour of hypothetical projects, and to allow researchers to view the implications of their assumptions, it can be easily customised and extended to become a tool for analysing and predicting the behaviour of actual projects.