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authors Mitchell, William J., Liggett, Robin S. and Tan, Milton
year 1988
title The Topdown System and its use in Teaching - An Exploration of Structured, Knowledge-Based Design
source Computing in Design Education [ACADIA Conference Proceedings] Ann Arbor (Michigan / USA) 28-30 October 1988, pp. 251-262
summary The Topdown System is a shell for use in developing simple (but we believe non-trivial) knowledge-based CAD systems. It provides a data structure, graphics capabilities, a sophisticated user interface, and programming tools for rapid construction of knowledge bases. Implementation is for Macintosh, Macintosh II, IBM PC/AT, PS12, and Sun workstations.

The basic idea is that of top-down design - beginning with a very abstract representation, and elaborating that, in step-by-step fashion, into a complete and detailed representation. The basic operations are real-time parametric variation of designs (using the mouse and slide bar) and substitution of objects. Essentially, then, a knowledge-base in Topdown implements a kind of parametric shape grammar.

The main applications of Topdown are in introductory teaching of CAD, and (since it provides a very quick and easy way for a user to develop detailed geometric models) to provide a uniform front-end for a variety of different applications. The shell, and some example knowledge-bases, are publicly available.

This paper discusses the principles of the Topdown Shell, the implementation of knowledge bases within it, and a variety of practical design applications.

series ACADIA
email wjm@MIT.EDU
full text file.pdf (1,190,960 bytes)
references Content-type: text/plain
details citation check to select
100%; open Gombrich, E.H. (1960) Find in CUMINCAD Art and Illusion - a study in the psychology of pictorial representation , Princeton University Press, Princeton, NJ.
100%; open Mitchell, W.J., Liggett, R.S. and Kvan, T. (1987) Find in CUMINCAD The Art of Computer Graphics Programming , Van Nostrand Reinhold, N.Y.

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