An investigation of the merging and collapsing of software

We explore the use of complex networks for understanding of the interaction of computer software applications written in the Java object-oriented language with the "library classes" that they use (those provided by the Java Runtime Environment) as, essentially, a merged network of classes. The dependence of the software on the library is quantified using a recently introduced model that identifies phases close to a second-order phase transition existing in scale-free networks. An example is given of a piece of software whose class network collapses without the presence of the library classes, providing validation of a novel structural coupling measure; Rcoupling. The structural properties of the merged software-Java class networks were found to correlate with the proportion of Java classes contained within the subset delimited by Rcoupling. A mechanism for the preservation of the software class network is also provided for the cases studied where the removal of the library classes does not cause collapse.