  Graphs have been widely used to model different information networks, such as
the Web, biological networks and social networks (e.g. Twitter). Due to the
size and complexity of these graphs, how to explore and utilize these graphs
has become a very challenging problem. In this paper, we propose, VCExplorer, a
new interactive graph exploration framework that integrates the strengths of
graph visualization and graph summarization. Unlike existing graph
visualization tools where vertices of a graph may be clustered into a smaller
collection of super/virtual vertices, VCExplorer displays a small number of
actual source graph vertices (called hubs) and summaries of the information
between these vertices. We refer to such a graph as a HA-graph (Hub-based
Aggregation Graph). This allows users to appreciate the relationship between
the hubs, rather than super/virtual vertices. Users can navigate through the
HA- graph by "drilling down" into the summaries between hubs to display more
hubs. We illustrate how the graph aggregation techniques can be integrated into
the exploring framework as the consolidated information to users. In addition,
we propose efficient graph aggregation algorithms over multiple subgraphs via
computation sharing. Extensive experimental evaluations have been conducted
using both real and synthetic datasets and the results indicate the
effectiveness and efficiency of VCExplorer for exploration.
