The adaptive, flexible approach….views projects as dynamic, unstable, and hard-to-predict processes. It assumes that changes will take place during project execution – changes in the environment, the business, the markets, technologies, and people. According to this approach, project plans must be adapted to changes that could not have been predicted at the outset. Thus, a project plan is not a fixed document that is prepared once for the entire project. Rather, project plans are dynamic, living entities that evolve as the project progresses and change when new information is revealed.
The solution is simple. Rather than “plan your work, and work your plan,” you should follow a process more like “plan some of your work, work that plan, and then replan the next piece of your work, and so on.” Rather than prepare detailed plans at the outset, you should plan only for those things that you are highly certain will not change. The idea is to replace the “management as planned” concept with “management as planned and replanned.” You should see a project as a continuous process of action and reflection, followed by more action.
– Aaron J Shenhar and Dov Dvir from Reinventing Project Management, p. 176