Context-Sensitive Interaction Mining
Email Interaction Graph

Email remains one of the most important communication tools in today's business environments. Email-based communications (i.e., interaction networks) are important to study fundamental interaction patterns between people. An important question in networks -including the internet, biological networks, and email interactions - is the discovery of important nodes.
Here an undirected subgraph of the Enron email corpus is shown:

The figure visualizes a small portion of the entire interaction graph (the graph comprises more than 1000000 nodes) based on importance rankings of each user. The diameter of each node is proportional to the relative importance. Fundamental indicators for importance rankings are metrics such as interaction intensity based on communications of people who also interact with other important people (cf. PageRank).