@article{eprints1097, pages = {28006}, publisher = {IOPscience}, journal = {EPL (Europhysics Letters)}, month = {January}, number = {2}, volume = {81}, year = {2008}, title = {Taxonomy and clustering in collaborative systems: the case of the on-line encyclopedia Wikipedia}, author = {Andrea Capocci and Francesco Rao and Guido Caldarelli}, url = {http://eprints.imtlucca.it/1097/}, abstract = {In this paper we investigate the nature and structure of the relation between imposed classifications and real clustering in a particular case of a scale-free network given by the on-line encyclopedia Wikipedia. We find a statistical similarity in the distributions of community sizes both by using the top-down approach of the categories division present in the archive and in the bottom-up procedure of community detection given by an algorithm based on the spectral properties of the graph. Regardless of the statistically similar behaviour, the two methods provide a rather different division of the articles, thereby signaling that the nature and presence of power laws is a general feature for these systems and cannot be used as a benchmark to evaluate the suitability of a clustering method.}, keywords = {PACS: 89.75.Hc Networks and genealogical trees; 89.75.Fb Structures and organization in complex systems; 89.75.-k Complex systems} }