Avoid Standing Waves

One of the odd side-effects of keeping your plans up-to-date is the standing wave. In this situation, you always plan to update your plans over the next few weeks. Since projects that are behind schedule tend to get further behind schedule, this "update the plan soon" strategy requires larger and larger resources to be applied over the next few weeks. The wave gets larger and larger with no corrective action taken. Rescheduling and replanning in general require action, not just promises that things will be fixed soon. Just because you are only a few days behind, don't put off updating the plan. All projects fall behind one day at a time.

Reference:

Brooks, F., The Mythical Man-Month, Reading, MA: Addison-Wesley, 1975.

Keep Your Plan Up-to-date

You must plan a software project; however, having an out-of-date plan is even worse than having no plan at all. When you have no plan, you know you are out of control. When you have an out-of-date plan, you may naively think you are under control. So whenever circumstances change, update your plan. Such circumstances include changes to the requirements, a schedule slippage, a change in direction, finding excessive errors, or any deviation from the original conditions.

A well-written plan should enumerate the risks, the warning signs that the potential risk is becoming a threat, and contingency plans to put into place to reduce the threat. As a project progresses and predicted risks become threats, the contingency plans are implemented and the project plan is updated. The real challenge occurs when unforeseen changes occur. For these times, one often needs to replan the remainder of a project in its entirety, with new assumptions, new risks, new contingency plans, new schedules, new milestones, and so on.

Reference:

Reifer, D., "The Nature of Software Management: A Primer," Tutorial: Software Management, Washington, DC: IEEE Computer Society Press, 1986.