Monday, January 30, 2012

The Mythical Man-Month – Extracts VII

Source: The Mythical Man-Month

Importance of Milestones  in Big Projects

How does one control a big project on a tight schedule? The first step is to have a schedule. Each of a list of events, called milestones, has a date. Picking the dates is an estimating problem, discussed already and crucially dependent on experience.

For picking the milestones there is only one relevant rule. Milestones must be concrete, specific, measurable events, defined with knife-edge sharpness. Coding, for a counterexample, is "90 percent finished" for half of the total coding time. Debugging is "99 percent complete" most of the time. "Planning complete" is an event one can proclaim almost at will.

Concrete milestones, on the other hand, are 100-percent events. "Specifications signed by architects and implementers," "source coding 100 percent complete, keypunched, entered into disk library," "debugged version passes all test cases." These concrete milestones demark the vague phases of planning, coding, debugging.

Two interesting studies of estimating behavior by government contractors on large-scale development projects show that:

  1. Estimates of the length of an activity, made and revised carefully every two weeks before the activity starts, do not significantly change as the start time draws near, no matter how wrong they ultimately turn out to be.
  2. During the activity, overestimates of duration come steadily down as the activity proceeds.
  3. Underestimates do not change significantly during the activity until about three weeks before the scheduled completion.

Sharp milestones are in fact a service to the team, and one they can properly expect from a manager. The fuzzy milestone is the harder burden to live with. It is in fact a millstone that grinds down morale, for it deceives one about lost time until it is irremediable. And chronic schedule slippage is a morale-killer.

Under the rug

When a first-line manager sees his small team slipping behind, he is rarely inclined to run to the boss with this woe. The team might be able to make it up, or he should be able to invent or reorganize to solve the problem. Then why worry the boss with it? So far, so good. Solving such problems is exactly what the first-line manager is there for. And the boss does have enough real worries demanding his action that he doesn't seek others. So all the dirt gets swept under the rug.

But every boss needs two kinds of information:

  • Exceptions to plan that require action and
  • Status picture for education. For that purpose he needs to know the status of all his teams. Getting a true picture of that status is hard.

The first-line manager's interests and those of the boss have an inherent conflict here. The first-line manager fears that if he reports his problem, the boss will act on it. Then his action will preempt the manager's function, diminish his authority, foul up his other plans. So as long as the manager thinks he can solve it alone, he doesn't tell the boss.
Two rug-lifting techniques are open to the boss. Both must be used.

  • The first is to reduce the role conflict and inspire sharing of status.
  • The other is to yank the rug back.


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