Layers and Hierarchies in Real Virtual Networks

The virtual world is comprised of data items related to each other in a variety of contexts. Often such relations can be represented as graphs that evolve over time. Examples include social networks, co-authorship graphs, and the world-wide-web. Attempts to model these graphs have introduced the notions of hierarchies and layers, which correspond to taxonomies of the underlying objects, and reasons for object relations, respectively. In this paper we explore these concepts in the process of mining such naturallygrown networks. Based on two sample graphs, we present some evidence that the current models well fit real world networks and provide concrete applications of these findings. In particular, we show how hierarchies can be used for greedy routing and how separation of layers can be used as a preprocessing step to implement a location estimation application.