evolution of a modern software network

http://www.pnas.org/content/early/2011/11/14/1115960108

Evolution of a modular software network

Miguel A. Fortunaa,b, Juan A. Bonachelaa, and Simon A. Levina,1

aDepartment of Ecology and Evolutionary Biology, Princeton University,
Princeton, NJ 08544-1003; bIntegrative Ecology Group, Estación Biológica de
Doñana–Consejo Superior de Investigaciones Cientificas, 41092 Seville, Spain

Contributed by Simon A. Levin, September 30, 2011 (sent for review June 30,
2011)

Abstract

“Evolution behaves like a tinkerer” (François Jacob, Science, 1977). Software
systems provide a singular opportunity to understand biological processes
using concepts from network theory. The Debian GNU/Linux operating system
allows us to explore the evolution of a complex network in a unique way. The
modular design detected during its growth is based on the reuse of existing
code in order to minimize costs during programming. The increase of
modularity experienced by the system over time has not counterbalanced the
increase in incompatibilities between software packages within modules. This
negative effect is far from being a failure of design. A random process of
package installation shows that the higher the modularity, the larger the
fraction of packages working properly in a local computer. The decrease in
the relative number of conflicts between packages from different modules
avoids a failure in the functionality of one package spreading throughout the
entire system. Some potential analogies with the evolutionary and ecological