Spatial is the largest by far. Stretching back to 1976, when Negroponte and three others proposed the Spatial Data Management System, researchers have been captivated by the dream geography of data space. They all face the same problem, however, that has rendered the desktop obsolete: scaling. How do you represent such a huge space on such a small screen?
A second, much smaller, group of research has focused on semantic organizations. Instead of sorting files in terms of folders and location, these schemes organize files by content. It’s similar to how search engines such as AltaVista and HotBot organize the Web. The best example of this was a short-lived project at MIT called the Semantic File System, which eliminated the directories in Unix and replaced them with means to efficiently address files by their content.
The third type of organization is represented by Vannevar Bush’s Memex, Ted Nelson’s Xanadu, and today’s World Wide Web: documents are organized in relation to other documents by means of links. This kind of networked organization allows for far richer structures than the simple tree hierarchy formed by folders on a desktop.