Applying Process Simulation to Software Project Scheduling

Good project scheduling is an essential yet extremely hard task in software management practice. The time needed to complete a development activity usually is known only roughly. Often, the completion of an activity is delayed due to unanticipated rework. In this paper, we show how process simulation can be utilized in order to support software managers in finding good schedules for their projects. We present a novel, discrete simulation model for software projects which explicitly takes a scheduling policy as input. The model represents task assignments, staff skill levels, component coupling, and rework caused by design changes. The simulation model is implemented in the ModL language of the general-purpose graphical simulation tool EXTEND [4]. As a first application of our project simulation model, we systematically study the performance of various so-called list policies for a sample project. The simulations quickly show what impact each list policy has on the expected progress and completion time of the sample project. We also provide a detailed analysis of the task assignments which actually occur in the simulations. The analysis clearly identifies the reasons why the list policies perform as observed.