1990 CoDraw is a two-dimensional CAD program built to explore interactive graphical constraints in design software. A designer applies spatial relationships (e.g., aligned objects, offsets, parallel lines) to drawing elements and the computer maintains them. Most important, the system is object-oriented and open-ended. End-users extend CoDraw’s built-in relationships with a simple spreadsheet to define new constraints. CoDraw also included a number of other innovative features for constraint based programming and design. A designer can view and edit the assembly structure of the design as a graph,extend the class-instance system interactively on the fly, and use built in collision detection to avoid interference among solid elements.

1992 Graphical Constraints in CoDraw, Gross, M.D., IEEE Workshop on Visual Languages, Seattle, pp. 81-87. [pdf]
1990 Relational Modeling: A Basis for Computer-Assisted Design, Gross, M.D., in McCullough, Mitchell and Purcell, eds., The Electronic Design Studio, Cambridge, MA: MIT Press, pp. 123-136. [pdf]