A comparison of model-based and judgment-based release planning in incremental software projects

Numerous factors are involved when deciding when to implement which features in incremental software development. To facilitate a rational and efficient planning process, release planning models make such factors explicit and compute release plan alternatives according to optimization principles. However, experience suggests that industrial use of such models is limited. To investigate the feasibility of model and tool support, we compared input factors assumed by release planning models with factors considered by expert planners. The former factors were cataloged by systematically surveying release planning models, while the latter were elicited through repertory grid interviews in three software organizations. The findings indicate a substantial overlap between the two approaches. However, a detailed analysis reveals that models focus on only select parts of a possibly larger space of relevant planning factors. Three concrete areas of mismatch were identified: (1) continuously evolving requirements and specifications, (2) continuously changing prioritization criteria, and (3) authority-based decision processes. With these results in mind, models, tools and guidelines can be adjusted to address better real-life development processes.