Issue
EPL
Volume 77, Number 2, January 2007
Article Number 20002
Number of page(s) 6
Section General
DOI http://dx.doi.org/10.1209/0295-5075/77/20002
Published online 09 January 2007
EPL, 77 (2007) 20002
DOI: 10.1209/0295-5075/77/20002

Crossover from endogenous to exogenous activity in open-source software development

S. Valverde

Complex Systems Lab (ICREA-UPF), Barcelona Biomedical Research Park (PRBB-GRIB) - Dr. Aiguader 88, 08003 Barcelona, Spain


received 21 September 2006; accepted in final form 14 November 2006; published January 2007
published online 9 January 2007

Abstract
We have investigated the origin of fluctuations in the aggregated behaviour of an open-source software community. In a recent series of papers (DE MENEZES M. A. and BARABÁSI A.-L., Phys. Rev. Lett., 92 (2004) 28701; 93 (2004) 68701; YOOK S. H. and DE MENEZES M. A., Europhys. Lett., 72 (2005) 541), de Menezes and co-workers have shown how to separate internal dynamics from external fluctuations by capturing the simultaneous activity of many system's components. In spite of software development being a planned activity, the analysis of fluctuations reveals how external driving forces can be only observed at weekly and higher time scales. Hourly and higher change frequencies mostly relate to internal maintenance activities. There is a crossover from endogenous to exogenous activity depending on the average number of file changes. This new evidence suggests that software development is a non-homogeneous design activity where stronger efforts focus in a few project files. The crossover can be explained with a Langevin equation associated to the cascading process, where changes to any file trigger additional changes to its neighbours in the software network. In addition, analysis of fluctuations enables us to detect whether a software system can be decomposed into several subsystems with different development dynamics.

PACS
05.70.-Ln - Nonequilibrium and irreversible thermodynamics.
89.65.-s - Social and economic systems.
05.10.-a - Computational methods in statistical physics and nonlinear dynamics.

© Europhysics Letters Association 2007