Design metrics and software maintainability: An experimental investigation

An empirical study was conducted into the relationship between various design metrics and software maintainability. This was based upon maintenance changes made to four different versions of a project management tool carried out by a total of 60 programmers. The overall conclusion from the investigation, was that accurate prediction of quality characteristics for single maintenance changes is extremely difficult. This is due to the many sources of variation—principally change type and programmer ability. Nevertheless, we show that measures of information flow local to specific modifications are significantly related to error rates, with a 600% greater probability of a residual error as a consequence of a change in a module with a high level of information flow-based coupling, than a module with a low level of coupling. Furthermore, we show that different types of change reveal marked variations in their relationships with the design metrics. Consequently, we argue that using robust statistical techniques and theoretically well-founded design metrics, engineering approximations are possible.