A mode is defined by the user when he pushes one or more buttons that appear to his left. These buttons are signals to the machine that state a major change in activity. Associated with each mode is a string of machine-defined or user-defined text (verbs) that appears as a menu of “light buttons.” Each mode has its own set of light buttons that denote related operations. The detection of one light button can change this menu of words, making endless the potential number of operations per context.
The graphic modes permit the handling of the ground plane, the ten-foot cubes, and their surfaces. TOPO displays a site plan, for example, which appears as a grid of altitudes that the designer can manipulate with his light pen in order to create a warped surface approximating his topography. DRAW, a separate mode, allows the manipulation of (1) viewing mode (orthographic, perspective), (2) viewing plane (scale, rotation, translation), (3) physical elements (solids, voids, roofs, people, trees, vehicles). In DRAW mode, when two cubes are placed tangent to each other, the adjoining surface is automatically removed, thus forming one continuous volume that is inherently part of an external membrane. Therefore, to qualify further external surfaces or add internal surfaces, the designer must enter a new context, SURFACE mode. In SURFACE mode, any of the six surfaces of the cube can be ascribed one of four (again abstracted and simplified) characteristics: solid (defining a major activity boundary), partition (a subdivision of a common usage), transparent, or absent. Each of these surface traits can be assigned with or without the attribute of “access.”
The next three rows of buttons are interdependent modes that require multiple button pushing. The combination of an operation with a context with a set of symbols yields a mode. At first these modes are primarily empty receptacles for the designer to employ to define his own light buttons. For example, the user may QUALIFY in the context of ACTIVities and press symbol button number one. At this point a cursor will appear on the right below the last word in the list of light buttons. He can then type a new word for future use in some operation, for example, f-o-o-t-b-a-l-l. As soon as he finishes typing “football,” a list of “generics” appears on the screen. These generics are a function of the context—in this case activities—and allow the designer to define his word by detecting the relevant qualifying words. In this example the generics describe age groups, times of day, noise levels, participation, and other activity characteristics that have a built-in meaning to the machine. Later, this user-made light button can be employed as a verb (footballizing a space) in an operational context of ASSIGNment or CALCULation.
Beyond assigning and calculating with symbols, generalized verbs can perform calculations and simulations within some context. For example, in CIRCULation mode a designer can have the machine simulate pedestrian travel between two points on the site. An x, the pedestrian, will prance across the screen trying to get from one point to the next, searching for a reasonable or at least feasible path. The machine will report the pedestrian’s distance and time of travel or else the impossibility of the trip through lack of enough elements with “access.” Similar simulations exist in the context of ELEMents for the path of the sun and for growth patterns.
The next row of buttons, the therapeutic ones, are instructional modes that are “intended to make the designer-machine interface as conversational and personal as possible, permitting the user to articulate himself in the privacy of himself” (Negroponte and Groisser, 1967a). The PANIC button, for example, summons instructions on the usage of other modes, directions on how to proceed, and an accounting mechanism that can be interrogated for computer time spent in dollars (often affording cause for greater panic). The therapeutic modes were often inconsistently designed. In truth, PANIC should never be depressed for reasons of total distress. In a true dialogue the machine should sense the designer panicking long before the button is pushed. PANIC, in fact, was erroneously designed as an alarm monologue rather than a teaching dialogue.
The remaining modes are primarily procedural ones that act in a janitorial fashion. STORE mode, as an example, permits design studies to reside in either short-term or long-term storage devices, to be given arbitrary names, and to be recalled in a few hundredths of a second (recalled by either name or time of creation).
Within these modes there is no predetermined sequence of usage; there is no presupposed chain of events. URBAN5 has one central “attention” mechanism that either listens to or hears from the designer, always giving him the opportunity to change his mind or restate a situation at any time. However, the reader should notice that the context, which is so important to intelligent behavior, is explicitly stated by the human designer and not, in URBAN5, implicitly discerned by the machine.