Measuring Flexibility in Software Project Schedules

The complexity of software projects is growing with the increasing complexity of software systems. The pressure to fit schedules within shorter periods of time leads to initial project schedules with a complex logic. These schedules are often highly susceptible to any subsequent delays in project activities. Thus, techniques need to be developed to determine the quality of a software project schedule. Most of the existing measures of schedule quality define the goodness of a schedule in terms of its network complexity. However, these measures fail to estimate the flexibility of a schedule, that is, the extent to which a schedule can withstand delays without requiring extensive changes. The relatively few schedule flexibility measures that exist in literature suffer from several drawbacks such as lack of a theoretical foundation, not having a definite scale and not being able to distinguish between schedules with similar network topologies. In this paper, we address these issues by defining two flexibility measures for software project schedules, namely path shift and value shift, which, respectively, predict the impact of changes in activity durations on the critical paths and the critical value of a schedule. Inspired by the notion of betweenness centrality, these measures are theoretically sound, have a well-defined scale, and require little computational effort. Furthermore, by several examples and two real-life software project case studies, we demonstrate that these measures outperform the existing flexibility measures in clearly discriminating between the flexibility of software project schedules having very similar topologies.