This did not happen overnight. Architects have slowly lost their "constructive consciousness" since the beginning of the 19 th century when science crept into architecture and placed the engineer beside it. Of course the introduction of steel as a visible element has evoked an intense discussion between leading architects. But this source of the architectural form derived from material disappears later on. As a consequence architects have become dependent on others to solve their construction problems. That way they have given away their ability to control the interaction between the perception and the materiality of a building. No surprise that today's buildings are falling apart in a figurative sense.

But it seems that for those who believe in a close connection between form and construction an occasion is coming up that may help them to solve the dilemma. The graphic possibilities and the reasonable price of the new computer hardware and software will lead to their use in the architectural design process. Computers force us, as we have learned by using them to draw our working-drawings, to structure the information. An intelligent structure is thereby a supposition for a successful use. Since one needs to structure the information anyway, then, why should we not use an architectural structure? Surely we do it better in our own way since it also means to structure our thinking in that way. The search for such a structure presents us a unique opportunity to think about the sense and the meaning of every single line and their affiliation to others or to think about the function of drawing in general. Rather than only perfect our ability to produce powerful images, this possibility may form the basis or a new interrelationship on a structural level between the "what" of building - the power of visions and images - and the "how" - the expression of technique. This will lead us to a more complete idea about architecture

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The building volume as it exists from outside and the space volume as it exists from inside are two possible ways to conceive a building. Through their simultaneous existence they are interrelated. Each of them is related to a separate set of references, for example the building volume is related to the outside space, the place or the city. Similar references to the space volumes can be an interpretation of significance, specific use, given functions or space requirements. They may be differentiated by such attributes as use, circulation, equipment or service space. Their aggregation may be formed by dialectic associations such as public/private, serve/served, extrovert/introvert, large/small, noisy/quiet. The building volume can be a result of the addition of space volumes; the space volume can be a result of the division of the building volume or they can have a dialectic relationship so that the space in-between becomes important.

With the building enclosure and space enclosure one changes from the direct expression of spaces to the indirect expression of describing them through the elements that define them. The interrelationships among the elements like walls, columns and ceilings become important. One interpretation of such an interrelationship may be seen as a superimposition of primary load bearing columns and non-loadbearing partition walls. The space enclosure reflects the mental spatial qualities of the building as well as the physical means of the building construction. Space enclosure and supporting structure are one basis to define the building enclosure. As a transition between inside and outside the building enclosure should refer to the various site conditions, the inner life of a building or the history of architecture as a collection of experiences. The selection of a particular enclosure system influences the way openings ought be placed and surfaces ought be treated. The distinction between different attributes of materiality may be used to form dialectic associations such as rough structure/finished structure, dry construction/wet construction or cast in place/prefabricated.

The supporting structure, as part of the enclosure system, expresses the relationship between the primary load bearing elements, such as walls, columns, ceilings and the roof. It pertains to the rough structure. The thoughts about a supporting structure arc not merely about calculation but also about intention or the feeling of what is correct. Through relationships to geometrical orders, the supporting structure has an expressive potential that affects many architects. Unfortunately it happens too often that the buildings lose their strength because the finished structure can not provide what the supporting structure promised. The supporting structure determines possible places and sizes of openings and is therefore an important limitation for enclosure, circulation and mechanical systems. The distinction between rough structure and finished structure may serve as an attempt to solve the problem of change and maintenance.

The circulation determines a special kind of relationship between different rooms as well as between different areas in the rooms themselves. It leads to a hierarchical organization of the spaces and to a zoning within the building volume. Circulation produces spaces as part of a sequence as well as spaces with their own identities. Circulation controls, together with the mechanical and utility systems, the section through their vertical and horizontal connecting elements. Through its demand for exceptions, the development of a circulation system influences strongly the design of the supporting structure.

Mechanical systems and utility systems form separate networks within the volume, which, similar to circulation, lead to the zoning of the building volume. The superimposition of the mechanical and utility systems on the supporting structure leads to a serious limitation in the design of each. The mechanical and utility systems control the three-dimensional articulation of the ceilings or the section of a building in general. The placement or the vertical elements form fixed points in what may be otherwise open space. With mechanical and utility systems the question of possible changes and maintenance becomes an evident issue.

Any one of the described factors or components can be seen as having an existence on two different levels of operation. On the mental level one has to associate the different elements to one of the components. The interrelationships among the elements and among the components is important. One operates with concepts, diagrams and schemes. I his level offers the possibility to convert specific design problems into existing types of problems and typical paths to find solutions. It is not necessary to know what the "things" are, but to know the rules of their interaction. An example from the building assembly course at the ETH-Zurich may illustrate how possible relationships between supporting structure and enclosure system can be shown so that students may understand the complex unity of a building through the figurative demonstration of its disassembly. To define the language and the rules of interaction among the components and among the elements would be one of the main issues of education: so that on the physical level, the level of production, the fragmented technical knowledge can ordered and understood in its entirety. At this level one operates with working (drawings, specifications, cost estimations, contracts and time constraints. The rules of the materials and their application are important. To reach an internal coherence one has to be conscious about the initial association of each element. Too often this relationship disappears in the professional realm because these associations are not apparent for all participants. The design process model may, through its structure, offer the architects the ability to communicate their essential thoughts, so that the basic design ideas can he transferred to the working drawings, rather than losing some of the ideas with every new start made in another scale on a blank sheet of paper.

The housing project St. Alban-Tal, Basle, Switzerland may serve as an example to illustrate how the interrelationships among the different factors of order can be visualized and used to clarify architectural decisions. The diagram of the spatial organization in both buildings is similar: the bedrooms are a series of equal cells forming a layer in the back of each flat and the living areas form another less defined layer in the remaining space. The supporting structure of the larger house is constituted by two boxes; one contains the living areas and the other the bedrooms. The space between the two boxes is reserved for circulation and service areas. The space enclosure of the bedrooms is constituted by non-loadbearing partition walls which are connected to the walls of the supporting structure. The partition walls of the living areas form, with their disconnection from the box, an internal circulation row along the facade. The supporting structure of the smaller house is a skeleton. On the bedroom side columns with a square shape show their ability to be connected with the non-loadbearing enclosure walls. In the living area the columns are circular to show their independence from the remaining enclosure. The two different approaches of space enclosure are reflected by the way the facades and their openings are treated. From outside one can read that the facade of the living areas is non-loadbearing by the way the openings are placed and the way the facade is disconnected from the ground. The less specific inside, symbolized by the free standing columns, goes together with the free composition of the openings outside as a response to the existing diversity of the city which has developed over time. The facade oriented towards the millpond as a concrete grid reflects the stronger definition of the spaces behind. If the information is properly stored, we can show how the association of the different building parts and therefore their treatment can be controlled separately, like the supporting structure or the non-loadbearing elements of the space enclosure.

Any one of the proposed factors and any one of the Ievels may serve as a starting point for the design process. Each one may serve as an analogy or a filter or the reality. All together, they constitute an inner structural relationship on a conceptual level - all essential interdependence of design and technique. Without this the idea of a building would be either incomplete, banal or chaotic. The associative systematic thinking that stands behind this design process model is analogous to the way the cognitive process is exhibited in set theory. The paintings of Carlo Aloe shows the polymorphic aspects of urban reality in different layers of significance. Similarly we have to identify our layers of significance in our view of architecture. Also, we have to identify the members of these set that arc related in a logical way. We have to know the set and its members.

Emil Rysler