Researchers at the University of North Carolina at Chapel Hill developed the Writing Environment (WE), a hypertext system based on a cognitive model of the communication process [Smith et al., 1987]. This model explains reading as the process of taking linear streams of text, comprehending it by structuring the concept hierarchically, and absorbing into long-term memory as a network. Writing is seen as a reverse process: A loosely structured network of internal ideas and external sources is first organized into an appropriate hierarchy or outline which is then translated into a linear stream of words, sentences, paragraphs, sections, and chapters [Smith et al., 1987].
WE was designed to support the process of writing. It contains two major view windows, one graphical and another hierarchical along with commands. The graphical windows allows the user to loosely structure their ideas in terms of nodes. As some conceptual structure begins to emerge, the writer can transfer the nodes into the hierarchy window which has specialized commands for tree operations. WE uses a relational database for the storage of nodes and links in the network. There are three other windows: an editor window, a query window, and a window to control system modes and the current working set of nodes. WE can be used both as a hypertext system as well as an authoring system with advanced graphical, direct manipulation structure editing capabilities [Conklin, 1987].
Other notable systems include: HES and FRESS from Brown University, MCC's gIBIS.