Determining the Intrinsic Structure of Public Software Development History

TL;DR

This study explores the intrinsic network structure of the entire corpus of public version control system data to understand its topology and inform analysis methods, using large-scale graph analysis techniques.

Contribution

It provides an initial exploration of the network topology of public software development history using large-scale graph analysis of VCS data from Software Heritage.

Findings

Analysis of degree distributions and their scale-free properties

Distribution patterns of connected component sizes

Shortest path length distributions in the graph

Abstract

Background. Collaborative software development has produced a wealth of version control system (VCS) data that can now be analyzed in full. Little is known about the intrinsic structure of the entire corpus of publicly available VCS as an interconnected graph. Understanding its structure is needed to determine the best approach to analyze it in full and to avoid methodological pitfalls when doing so. Objective. We intend to determine the most salient network topol-ogy properties of public software development history as captured by VCS. We will explore: degree distributions, determining whether they are scale-free or not; distribution of connect component sizes; distribution of shortest path lengths.Method. We will use Software Heritage-which is the largest corpus of public VCS data-compress it using webgraph compression techniques, and analyze it in-memory using classic graph algorithms. Analyses will be performed both on the full graph and on relevant subgraphs. Limitations. The study is exploratory in nature; as such no hypotheses on the findings is stated at this time. Chosen graph algorithms are expected to scale to the corpus size, but it will need to be confirmed experimentally. External validity will depend on how representative Software Heritage is of the software commons.