Network Visualization by Meaningful Substrates

Networks have remained a challenge for information visualization designers because of the complex issues of node and link layout coupled with the rich set of tasks that users present. This paper offers a five-layer hierarchy of network visualization situations with associated tasks: from simple node and link situations to more elaborate situations involving node labels, directed links, node attributes, and link attributes. Then, it offers a strategy based on tying node placement to node attributes within nonoverlapping regions. These user-defined meaningful substrates enable users to easily see which links remain within a region or cross to other regions. Link visibility is controlled by check boxes so that selected subsets of links can be displayed. To further limit display clutter, users can set sliders to control which nodes within a region have their edges visible. We illustrate our meaningful substrate approach in a modest example with legal precedents for 49 cases with 368 precedents, and show these in our implementation of NVMS 1.0.