A Node Aggregation Strategy to Reduce Complexity of Network Visualization using Semantic Substrates

Semantic substrates are spatial templates for networks, wherenodes are grouped into regions and laid out within each region
according to one or more node attributes. Analysts’ ability to
design their own substrates leads to a different approach than
other more automatic approaches to layout nodes (force-directed,
circular, etc.). While the semantic substrate approach provides
more interpretable node locations, sometimes a set of nodes is
compressed into a small space on the display, leading to node
overlap. In this paper, we significantly improve this situation by
introducing the node aggregation mechanism in the context of
semantic substrates. We illustrate this functionality in a document
citation network and provide pros and cons of the approach. We
conclude with guidelines and future directions for this research.
Throughout the paper, examples are illustrated with NVSS 3.0,
the network visualization tool developed to explore the semantic
substrate idea.