Abstract
Mining relational data often boils down to computing clusters, that is finding sub-communities of data elements forming cohesive sub-units, while being well separated from one another. The clusters themselves are sometimes termed "communities" and the way clusters relate to one another is often referred to as a "community structure". Methods for identifying communities or subgroups in network data is the focus of intense research is different scientific communities and for different purposes. The present paper focuses on two novel algorithms producing multilevel community structures from raw network data. The two algorithms exploit an edge metric extending Watts's clustering coefficient to edges of a graph. The full benefit of the method comes from the multilevel nature of the community structure as it facilitates the visual interaction and navigation of the network by zooming in and out of components at any level. This multilevel navigation proves to be useful when visually exploring a network in search for structural patterns.