A Model to Understand the Building and Running Inter-Dependencies of Software

The notion of functional or modular dependency is fundamental to understand the architecture and inner workings of any software system. In this paper, we propose to extend that notion to consider dependencies at a larger scale, between software applications (usually programs or libraries themselves). These dependencies, which we call inter-dependencies are of exceptional importance in free an open source software (FOSS), where it is common to build new applications by taking advantage of a rich and complex environment of programs and libraries whose functionality is available. To explore this concept, a methodology and visualization for studying inter-dependencies of a complex software system is presented and applied to one of the largest distributions of FOSS: Debian GNU/Linux.