title: Self-organization versus hierarchy in open-source social networks.
abstract: Complex networks emerge under different conditions including design (i.e., top-down decisions) through simple rules of growth and evolution. Such rules are typically local when dealing with biological systems and most social webs. An important deviation from such a scenario is provided by groups, collectives of agents engaged in technology development, such as open-source communities. Here we analyze their network structure, showing that it defines a complex weighted network with scaling laws at different levels, as measured by looking at e-mail exchanges. We also present a simple model of network growth involving nonlocal rules based on betweenness centrality. Our weighted network analysis suggests that a well-defined interplay between the overall goals of the community and the underlying hierarchical organization play a key role in shaping its dynamics.
authors.affiliation: ICREA-Complex Systems Laboratory, Universitat Pompeu Fabra, Dr. Aiguader 80, 08003 Barcelona, Spain.
authors.forename: Sergi
authors.initials: S
authors.lastname: Valverde
authors.forename: Ricard V
authors.initials: RV
authors.lastname: Solé