| Designers work by associating abstract concepts with graphic representations. For example, an architect may associate the concept "wall" with the drawing of a rectangle. At the early stages of the design process, the concept associated with a graphic representation may be relatively ambiguous. The "wall" may be of undetermined materials, construction, elevation and structure. In other words, the wall may be a kind of marble wall, or a kind of brick wall, or a kind of wood frame wall, etc. It may be transparent, translucent or opaque. It may be load bearing or non-load bearing. These alternative possibilities may exist in the mind of the architect. The alternatives may also be annotated on an architectural drawing. However, the typical computer aided design system of today would not contain any database reference to the wide set of possible kinds of objects that the rectangle could be.;In this dissertation, a computer aided design system is developed which provides for geometrical modeling and which accounts for ambiguity. A "conceptual structure" is provided in which an ambiguous "child" object may inherit attributes from many alternative kinds of "parent" objects. The "conceptual structure" can accommodate a design process through which a "child" object such as "wall" can become less ambiguous over time. The end of this process is the detailed specification of the final designed object.;The computer aided design system adapts the the artificial intelligence techniques of "frames", and "multiple-inheritance". It also adapts the conventional computer aided design techniques of "instantiation", and "parametric variation". The system is applied to a set of case studies, and tested with a focus on raytracing architectural objects.;Within chapter 1, the rationale for a "conceptual structure" is outlined with some examples. Chapter 2 provides a detailed description of the components of a conceptual structure. Chapter 3 relates classification systems used in architecture to the use of classification within a conceptual structural. Chapter 4 describes "conceptual structure" with respect to the design process. Within chapters 5 and 6, case studies are developed after some historically well known works of architecture. Chapter 7 compares the "conceptual structure" with other knowledge representation schemes that have been developed for computer aided design. Working examples of the computer aided design system are provided throughout the text. |
