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AKSOE: Physik sozio-ökonomischer Systeme
AKSOE 10: Poster Session (posters are expected to be displayed the full day 8:30-18:00)
AKSOE 10.56: Poster
Mittwoch, 29. März 2006, 16:00–18:00, P2
Directory trees created by computer users: Individuality vs. universality — •Konstantin Klemm1, Victor M. Eguiluz2, and Maxi San Miguel2 — 1Dept. of Bioinformatics, Leipzig University, Germany — 2IMEDEA (CSIC-UIB), Palma de Mallorca, Spain
We describe the topological structure and the underlying organization principles of the directories created by users of a computer cluster when storing their own files. For each of the 63 observed users, the branching ratio (number of directories with the same parent) exhibits a broad, typically scale-free distribution with a non-universal exponent. Thus users can be distinguished by the degree exponent of the scale-free trees they create. The size distribution of the branches (subtrees below the root) decays algebraically with a universal exponent -2. These scaling properties and further observations are captured by a model of incremental tree growth [1]. The single parameter of the model interpolates between agglomeration into star-like structures and fully random attachment that leads to deep hierarchies. The alignment between model and empirical trees reveals the universal features of trees created independently and unrestrictedly by different users. Individual differences of tree construction boil down to a single real-valued parameter that is extracted by the alignment.
[1] Konstantin Klemm, Victor M. Eguiluz, Maxi San Miguel, Phys. Rev. Lett. 95, 128701 (2005).