This great church is an incomparable work of art. There is neither aridity nor confusion in the tenets it sets forth. . , ,
It is the zenith of a style, the work of artists who had understood and assimilated all their predecessors’ successes, in complete possession of the techniques of their times, but using them without indiscreet display nor gratuitous feats of skill.
It was Jean d ‘Orbais who undoubtedly conceived the general plan of the building, a plan which was respected, at least in its essential elements, by his successors. This is one of the reasons for the extreme coherence and unity of the edifice.
REIMS CATHEDRAL GUIDEBOOK
The typical situation for a cathedral building is being made during several generations by several builders, where each period shows the ideas and “improvements” of those in command at that moment.
The Reims Cathedral is the counterexample: the building integrity was achieved by the self-abnegation of eight generations of builders whom sacrificed some of his ideas in benefit for the construction pure design.
Even though they have not taken centuries to build, most programming systems reflect conceptual disunity far worse than that of cathedrals. Usually this arises not from a serial succession of master designers, but from the separation of design into many tasks done by many men.
Conceptual integrity is the most important consideration in system design. It is better to have a system omit certain anomalous features and improvements, but to reflect one set of design ideas, than to have one that contains many good but independent and uncoordinated ideas.
Achieving Conceptual Integrity
The purpose of a programming system is to make a computer easy to use.
Ease of use is enhanced only if the time gained in functional specification exceeds the time lost in learning, remembering, and searching manuals. With modern programming systems this gain does exceed the cost, which did not happen in software development old days. Because ease of use is the purpose, the ratio of function- conceptual complexity is the ultimate test of system design. Neither function alone nor simplicity alone defines a good design.
For a given level of function, however, that system is best in which one can specify things with the most simplicity and straightforwardness.
It is not enough to learn the elements and rules of combination; one must also learn the idiomatic usage, a whole lore of how the elements are combined in practice. Simplicity and straightforwardness proceed from conceptual integrity. Every part must reflect the same philosophies and the same balancing of desiderata.
Every part must even use the same techniques in syntax and analogous notions in semantics. Ease of use, then, dictates unity of design, conceptual integrity.
Aristocracy and Democracy
Conceptual integrity in turn dictates that the design must proceed from one mind, or from a very small number of agreeing resonant minds. Schedule pressures, however, dictate that system building needs many hands. Two techniques are available for resolving this dilemma.
- Division of labour between architecture and implementation.
- The Surgical Team structuration
The separation of architectural effort from implementation is a very powerful way of getting conceptual integrity on very large projects. Complete and detailed specification of the user interface. (For the entire system it is the union of the manuals the user must consult to do his entire job).
The architect of a system has to bring professional and technical knowledge to bear in the unalloyed interest of the user, as opposed to the interests of the salesman, the fabricator, etc.
“Where architecture tells what happens, implementation tells how it is made to happen.”
In regard to the deeply emotional question of aristocracy versus democracy:
- Are not the architects a new aristocracy, an intellectual elite, set up to tell the poor dumb implementers what to do?
- Yes, in the sense that there must be few architects, their product must endure longer than that of an implementer, and the architect sits at the focus of forces which he must ultimately resolve in the user’s interest. If a system is to have conceptual integrity, someone must control the concepts. That is an aristocracy that needs no apology.
- No, because the setting of external specifications is not more creative work than the designing of implementations. It is just different creative work. The design of an implementation, given an architecture, requires and allows as much design creativity, as many new ideas, and as much technical brilliance as the design of the external specifications.
- Has not all the creative work been sequestered for this elite, leaving the implementers as cogs in the machine?
- Won’t one get a better product by getting the good ideas from all the team, following a democratic philosophy, rather than by restricting the development of specifications to a few?
- Not only the architects will have good architectural ideas. Often the fresh concept does come from an implementer or from a user. However, the conceptual integrity of a system determines its ease of use. Good features and ideas that do not integrate with a system’s basic concepts are best left out.
- If there appear many such important but incompatible ideas, one scraps the whole system and starts again on an integrated system with different basic concepts.
The external provision of an architecture enhances, not cramps, the creative style of an implementing group. They focus at once on the part of the problem no one has addressed, and inventions begin to flow. In an unconstrained implementing group, most thought and debate goes into architectural decisions, and implementation proper gets short shrift.
What Does the Implementer Do While Waiting?
“It is a very humbling experience to make a multimillion-dollar mistake, but it is also very memorable”
When it is proposed that a small architecture team in fact write all the external specifications for a computer or a programming system, the implementers raise three objections:
- The specifications will be too rich in function and will not reflect practical cost considerations.
- The architects will get all the creative fun and shut out the inventiveness of the implementers.
- The many implementers will have to sit idly by while the specifications come through the narrow funnel that is the architecture team.
In the computer systems business the pace is quicker than in construction (where design comes first, building comes after), and one wants to compress the schedule as much as possible. How much can specification and building be overlapped?
The total creative effort involves three distinct phases: architecture, implementation, and realization, which can in fact begun in parallel and proceed simultaneously. Meanwhile, on the realization level there is much to be done also. Programming has a technology, too. Much work must be done on subroutine conventions, supervisory techniques, searching and sorting algorithms.
Conceptual integrity does require that a system reflect a single philosophy and that the specification as seen by the user flow from a few minds. Because of the real division of labour into architecture, implementation, and realization, however, this does not imply that a system so designed will take longer to build. Experience shows the opposite, that the integral system goes together faster and takes less time to test. In effect, a widespread horizontal division of labour has been sharply reduced by a vertical division of labour, and the result is radically simplified communications and improved conceptual integrity.