The user interface of a diagram-drawing program, DIAG2, is described. The user is provided with three basic constructs: the straight line, the segment of a circle and the block of text. These constructs may be assembled into larger groups. Thus a diagram can be built up in a hierarchical manner by the user. DIAG2 performs the unwrapping operations necessary to decompose the diagram into a set of straight line segments, which can be output to the appropriate display peripheral. No intelligence is required in the graphics device itself. © 1984.
Brown, A. D. (1984). Computer-aided hierarchical diagrams. Computer-Aided Design, 16(5), 249–252. https://doi.org/10.1016/0010-4485(84)90082-4