Executable Drawings: the Computation of Digital Architecture

Architectural designs are principally represented by drawings. Usually, each drawing corresponds to one design or aspects of one design. On the other hand, one executable drawing corresponds to a set of designs. These drawings are the same as conventional drawings except that they have computer code or programs embedded in them. A specific design is the result of the computer executing the code in a drawing for a particular set of parameter values. If the parameters are changed, a new design or design variation is produced. With executable drawings, a CAD system is also a program editor. A designer not only designs by drawing but also programming. It fuses two activities: the first, drawing, is basic in architectural practice, and the second, progamming, or specifying the relation of outputs from inputs, is basic in computer system development. A consequence of executable drawings is that architectural form is represented by graphical entities (lines or shapes) as well as computer code or programs. This type of architecture we call digital architecture. Two simple examples are presented: first, the design of a building in terms of an executable drawing of the architects, Sangallo the Younger and Michelangelo, and second, a description of an object oriented implementation of a preliminary prototype of an executable drawing system written in 1997 which computes a simple office layout