Lincoln and Whitman during the Civil War (now known as “Civil War Washington: Studies in Transformation”) will be (as of mid-2007, “is”) a web site that emphasizes geo-spatial data, that is, historical data linked to spatial coordinates that are also represented by historical maps. But Lincoln-Whitman at the time of this post was a database that represented information entities. The information entities include broad information categories that are mappable by location: hospitals, forts, theaters, fugitive slave camps, etc. But the information entities also include people, events, associations of people, associations of events, and geographical data.
I drafted the SQL database entities (things) and relationships (ways in which data is linked) using a nifty application called GraphViz, a tool that can be used for drawing diagrams, including entity relationship (ER) diagrams. So one thing that Lincoln-Whitman was (at time of original post) is the attached chart, drawn in GraphViz. The chart is very large.
Note: To access “Civil War Washington: Studies in Transformation,” see
http://cdrh.unl.edu/civilwardc/ for the current public face of the project.