One embodiment of the present invention provides a computing system. The computing system includes a processor and a computer-readable storage medium. The computer-readable storage medium stores instructions which when executed by the processor cause the processor to perform a method. The method comprises assigning a vertex identifier of a first vertex to a second vertex in a graph based on an edge between the first vertex and the second vertex. The vertices represent elements in a data set, the edge represents a type and strength of relationship between the vertices. The method further comprises provisionally assigning each vertex to a vertex cluster associated with the vertex identifier, and converging the assignments based on a measure of cluster quality associated with all the vertex clusters. Each vertex cluster represents information of interest in the data set. One measure of clustering quality is called “modularity.”