It is a very humbling experience to make a multimillion-dollar mistake, but
it is also very memorable. I vividly recall the night we decided how to
organize the actual writing of external specifications for OS/360. The
manager of architecture, the manager of control program implementation, and
I were threshing out the plan, schedule, and division of responsibilities.
The architecture manager had 10 good men. He asserted that they
could write the specifications and do it right. It would take ten months,
three more than the schedule allowed.
The control program manager had 150 men. He asserted that they
could prepare the specifications, with the architecture team coordinating;
it would be well-done and practical, and he could do it on schedule.
Furthermore, if the architecture team did it, his 150 men would sit twiddling
their thumbs for ten months.
To this the architecture manager responded that if I gave the control
program team the responsibility, the result would not in fact be on time,
but would also be three months late, and of much lower quality. I did, and
it was. He was right on both counts. Moreover, the lack of conceptual
integrity made the system far more costly to build and change, and I would
estimate that it added a year to debugging time.
-- Frederick Brooks Jr., "The Mythical Man Month"