Visualization, causation, and history

History may be seen as a tapestry of interwoven events. The discourse structure of that tapestry may be identified and used to support visualization for examining and interacting with the tapestry of history. Specifically, we propose temporally constrained causal relationships as a key for organizing that tapestry. Because Events occur at different levels of granularity and similar ones may occur with cumulative effect, we introduce Trends. Trends are first-class objects; that is, in this model Trends may be causes of Events. To facilitate interaction with a rich tapestry of complex historical events such as the American Civil War, we also introduce Threads. These are chains of Events, and presentations of them may be considered a type of narrative. We describe a panel-oriented visualization interface that shows causal Threads of Events and Trends leading up to the Civil War. This initial prototype is intended to present history at the level of an intermediate textbook. Finally, we introduce a semi-formal notation for describing Events, Threads, and Trends, and propose directions for future research to refine the prototype that may enable broader, deeper, more flexible, and more complete exploration/presentation of historical materials.