Simply put, a diagram is a simplified drawing showing the appearance, structure, or workings of something; a schematic representation.
A diagram is a drawing that, stripped of all superfluous and distracting data, shows the general scheme or outline of an idea or object and its parts. It is a reductive graphic representation of the course or results of an action or process. Diagrams are enlisted at the formative moments of design to chart the potential relationship between concept and reality. In functioning as a constructive doodle, and concerned more with idea than appearance, diagrams are graphic representations of an idea being structured. However, the diagram is not the idea but a model of it; intended to define its characteristic features.
In order to develop an effective design model and to facilitate the evolution of forms in response to this model, a variety of diagrams, each with their own potential and conceptual set of rules that aid decision making, may be employed. These include ‘schematic’ and ‘operational diagrams· that are concerned with the relationship and orientation of the parts, and for visualizing changes over time. ‘Functional’, or ‘bubble diagrams, identify the proximity and relative size of the zones of activity, while ‘flow diagrams, like their operational counterparts, study possibilities that arise when movement is considered between one point and another.
Although diagrams can serve an explanatory function, clarifying form, structure or program to the designer, and notations map program in time and space, the diagram’s primary utility is as an abstract means of producing new models of organization.
Diagrams are graphic assemblage that specifies relationships between activity and form, organising the structure and distribution of functions. In architecture it is the best way to engage the complexity of the real.
Unlike classical theories based on imitation, diagrams do not map or represent already existing objects or systems but anticipate new organizations and specify yet to be realized relationships. The diagram is not simply a reduction from an existing order. Its abstraction is instrumental, and not an end in itself. Content is not embedded or embodied, but outlined and multiplied. Simplified and highly graphic, diagrams support multiple interpretations. Diagrams are not schemas, types, formal paradigms, or other regulating devices, but simply place-holders, instructions for action, or contingent descriptions of possible formal configurations. They work as abstract machines and do not resemble what they produce. – Stan Allen