Thursday, September 29, 2011

The Mythical Man-Month – Extracts IV

Source: The Mythical Man-Month

Architect - Needed Disciplines

Having in mind that we have separated responsibility for functional specification (Architect) from responsibility for building a fast, cheap product (Builder), now we have to answer the question of: how we will achieve the best outcome of our project? The fundamental answer is thoroughgoing, careful, and sympathetic communication between architect and builder.

Nevertheless there are little details that must to be observed for the Architect in order to get the ideal result, and these are:

Interactive Discipline

The architect has two possible answers when confronted with an estimate that is too high: cut the design or challenge the estimate by suggesting cheaper implementations. This latter is inherently an emotion-generating activity. The architect is now challenging the builder's way of doing the builder's job. For it to be successful, the architect must:

  • Remember that the builder has the inventive and creative responsibility for the implementation; so the architect suggests, not dictates;
  • Always be prepared to suggest a way of implementing anything he specifies, and be prepared to accept any other way that meets the objectives as well;
  • Deal quietly and privately in such suggestions;
  • Be ready to forego credit for suggested improvements.

Normally the builder will counter by suggesting changes to the architecture. Often he is right—some minor feature may have unexpectedly large costs when the implementation is worked out.

Self-Discipline—The Second-System Effect

An architect's first work is apt to be spare and clean. He knows he doesn't know what he's doing, so he does it carefully and with great restraint.

As he designs the first work, frill after frill and embellishment after embellishment occur to him. These get stored away to he used "next time." Sooner or later the first system is finished, and the architect, with firm, confidence and a demonstrated mastery of that class of systems, is ready to build a second system.

This second is the most dangerous system a man ever designs. The general tendency is:

  • To over-design the second system, using all the ideas and frills that were cautiously sidetracked on the first one.
  • Tendency to refine techniques whose very existence has been made obsolete by changes in basic system assumptions.

How does the architect avoid the second-system effect? Well, obviously he can't skip his second system. But he can be conscious of the peculiar hazards of that system, and exert extra self-discipline to avoid functional ornamentation and to avoid extrapolation of functions that are obviated by changes in assumptions and purposes.


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