Abstract for: Modeling rework cycle: comparing alternative formulations

Rework cycle is at the heart of modeling projects, one of the major application areas of system dynamics. In this paper we introduce a new formulation for rework cycle in which multiple defects may exist in a task. We compare the performance of this formulation with three others, two adopted from the system dynamics literature and one agent-based formulation. This comparative study illustrates the impact of assumptions about the nature of defects and the homogeneity of tasks on behavior of alternative models and provides information necessary for selecting rework cycle formulations effectively. The new formulation we introduce allows for capturing significant schedule over-runs due to a few tasks, with multiple defects, that may cycle through rework process multiple times. Its perfect mixing assumption, however, over-estimates final project quality. Sensitivity analysis informs the robustness of results to multiple project parameters. We discuss the implications for selecting robust formulations in modeling project dynamics.