Multi-level exploration of citation graphs

In previous work, we proposed a focus-based multi-level clustering technique. It consists in computing a particular clustered graph from a given graph and a focus. The resulting clustered graph is called multi-level outline tree. It is a tree whose meta-nodes are sub-sets of nodes. A meta-node is itself hierarchically clustered depending on its connectivity. In this paper we introduce a cluster cohesiveness measure to enhance the results of the previously proposed algorithm. We further propose an optimization of this algorithm to support fluid interaction when focus changes. Finally, we report the results of a case study that consists in applying the enhanced algorithm to citation graphs where documents are considered as vertices and citation links as edges.