Generic representations: an approach for modelling procedural and declarative knowledge of building types in architectural design

The building type is a knowledge structure that is recognised as an important element in the architectural design process. For an architect, the type provides information about norms, layout, appearance, etc. of the kind of building that is being designed. Questions that seem unresolved about (computational) approaches to building types are the relationship between the many kinds of instances that are generally recognised as belonging to a particular building type, the way a type can deal with varying briefs (or with mixed use), and how a type can accommodate different sites. Approaches that aim to model building types as data structures of interrelated variables (so-called “prototypes”) face problems clarifying these questions. The research work at hand proposes to investigate the role of knowledge associated with building types in the design process. Knowledge of the building type must be represented during the design process. Therefore, it is necessary to find a representation which supports design decisions, supports the changes and transformations of the design during the design process, encompasses knowledge of the design task, and which relates to the way architects design. It is proposed in the research work that graphic representations can be used as a medium to encode knowledge of the building type. This is possible if they consistently encode the things they represent, if their knowledge content can be derived, and if they are versatile enough to support a design process of a building belonging to a type. A graphic representation consists of graphic entities such as vertices, lines, planes, shapes, symbols, etc. Establishing a graphic representation implies making design decisions with respect to these entities. Therefore it is necessary to identify the elements of the graphic representation that play a role in decision making. An approach based on the concept of “graphic units” is developed. A graphic unit is a particular set of graphic entities that has some constant meaning. Examples are: zone, circulation scheme, axial system, and contour. Each graphic unit implies a particular kind of design decision (e.g. functional areas, system of circulation, spatial organisation, and layout of the building). By differentiating between appearance and meaning, it is possible to define the graphic unit relatively shape-independent. If a number of graphic representations have the same graphic units, they deal with the same kind of design decisions. Graphic representations that have such a specifically defined knowledge content are called “generic representations.” An analysis of over 220 graphic representations in the literature on architecture results in 24 graphic units and 50 generic representations. For each generic representation the design decisions are identified. These decisions are informed by the nature of the design task at hand. If the design task is a building belonging to a building type, then knowledge of the building type is required. In a single generic representation knowledge of norms, rules, and principles associated with the building type are used. Therefore, a single generic representation encodes declarative knowledge of the building type. A sequence of generic representations encodes a series of design decisions which are informed by the design task. If the design task is a building type, then procedural knowledge of the building type is used. By means of the graphic unit and generic representation, it is possible to identify a number of relations that determine sequences of generic representations. These relations are: additional graphic units, themes of generic representations, and successive graphic units. Additional graphic units defines subsequent generic representations by adding a new graphic unit. Themes of generic representations defines groups of generic representations that deal with the same kind of design decisions. Successive graphic units defines preconditions for subsequent or previous generic representations. On the basis of themes it is possible to define six general sequences of generic representations. On the basis of additional and successive graphic units it is possible to define sequences of generic representations in themes. On the basis of these sequences, one particular sequence of 23 generic representations is defined. The particular sequence of generic representations structures the decision process of a building type. In order to test this assertion, the particular sequence is applied to the office building type. For each generic representation, it is possible to establish a graphic representation that follows the definition of the graphic units and to apply the required statements from the office building knowledge base. The application results in a sequence of graphic representations that particularises an office building design. Implementation of seven generic representations in a computer aided design system demonstrates the use of generic representations for design support. The set is large enough to provide additional weight to the conclusion that generic representations map declarative and procedural knowledge of the building type