On automatically collectable metrics for software maintainability evaluation

In our work with industry partners as well as with students in seminars we noticed that many people often stick to 'aged' metrics when they want to evaluate the maintainability of software. They consider these metrics for this purpose without second thoughts, because the metrics are so present that almost every developer has at least heard the name and has some kind of knowledge about it. This smattering leads to an unreflected usage of theses metrics today without fully understanding them. To find suitable metrics for maintainability evaluation, we did a preliminary study, which indicated that still McCabe, Halstead and some kind of lines of code measurement dominate maintainability evaluation. We will discuss examples that question the ability of those metrics to reliably and automatically evaluate maintainability of software. Instead we will present metrics we consider more suitable to make solid statements about software maintainability. We conclude that our proposed metrics are better evaluators for maintainability because their impact on maintenance is clearer to interpret. Future work on metrics should carefully consider the use of 'aged' metrics.