URBAN5 handles qualities either explicitly or implicitly.
Beyond the traits of solid and void, each ten-foot cube (whether solid or void) has preallocated receptacles for ten characteristics that refer to aspects of sunlight, outdoor access, visual privacy, acoustical privacy, usability, direct access, climate control, natural light, flexibility, structural feasibility. All these qualities are implicitly ascribed to elements. In other words, without the user’s permission, intervention, or even awareness, URBAN5 automatically assigns the absence or presence of these features using a predefined geometry for each quality. (This geometry can be changed by the user at a later date when he is more familiar with the workings of the system.) This means that when a ten-foot cube is added (making a solid) or removed (making a void), URBAN5 tacitly rearranges the local and, if necessary, global characteristics. For example, the addition of an element not only casts shadows on other solids and voids but might obstruct another element’s natural light or visual privacy
Implicit qualities are occasionally reported to the designer (depending on their importance), but in most cases the designer must explicitly interrogate the cube to find its qualitative status. URBAN5 is more prone to divulge implicitly ascribed qualities when the neighboring influences are significant. Certain characteristics are strongly communicative, and their presence is directly transposable to neighboring elements or members of the same space (natural light, acoustical privacy). Other qualifications are less communicative (visual privacy, direct sunlight), and their influence is particularly local and is apt not to be posted.
Explicit qualities are assigned by the designer; they are the symbols that he has previously defined with the context-dependent generics. Each element can carry four symbols of any context. The designer can assign these symbols to a single element or enter a “flooding operation” to fill an entire “use space” (defined by solid walls) with the given symbol. For example, a single cube might be part of a set of “school” elements which are at the same time “a place to vote” elements which are, still further, part of a subset of “eating” and “auditorium” activities. In other words, a multiplicity of explicitly assigned symbols can exist for each cube. These traits are then cross-coupled with the implicit qualities of a space.
It is important to notice that the implicit and explicit assignment of attributes are sequential events. The machine ascribes certain qualities in response to the user adding or subtracting cubes; it is, in effect, an answer, even though it is not explicitly voiced. On the other hand, cross-coupling qualities, relating implicit qualities to explicit qualities, is a temporal event. This interaction forms the architect-machine search for consistency and equilibrium—a temporary state of no conflicts and no incompatibilities.