The fractal dimension metric and its use to assess object-oriented software quality

We present a study were software systems are considered as complex networks which have a self-similar structure under a length-scale transformation. On such complex software networks we computed a self-similar coefficient, also known as fractal dimension, using "the box counting method". We analyzed various releases of the publically available Eclipse software systems, calculating the fractal dimension for twenty sub-projects, randomly chosen, for every release, as well as for each release as a whole. Our results display an overall consistency among the sub-projects and among all the analyzed releases. We found a very good correlation between the fractal dimension and the number of bugs for Eclipse and for twenty sub-projects. Since the fractal dimension is just a scalar number that characterizes a whole system, while complexity and quality metrics are in general computed on every system module, this result suggests that the fractal dimension could be considered as a global quality metric for large software systems. Our results need however to be confirmed for other large software systems.