Planning is an unnatural process, it’s much more fun to get on with it. The real benefit of not planning is that failure comes as a complete surprise and is not preceded by months of worry.
‒ Sir John Harvey Jones
And of course
For which of you, intending to build a tower, sitteth not down first, and counteth the cost, whether he have sufficient to finish it? Lest haply, after he hath laid the foundation, and is not able to finish it, all the behold it begin to mock him, saying, This man began to build, and was not able to finish ―Luke 14:28-30
The Plan describes where we are going, the various paths we can take to reach our destination, and the progress or performance assessment points along the way to assure we are on the right path. These assessment points measures the “maturity” of the product or service against the planned maturity. This is the only real measure of progress – not the passage of time or consumption of money.
Without a Plan, the only purpose of the Schedule is to show the sequence of work, the dependencies between the work activities, and collecting progress the passage of time and consumption of money.
The Plan - actually the Integrated Master Plan - is the basis of the Integrated Master Schedule
This decomposition is not unique to the IMP/IMS paradigm. Without some form of decomposition of what “done” looks like, it is difficult to connect the work of the project to the outcomes of the project. This decomposition – which is hierarchical – provides the mechanism to increase cohesion and decrease coupling of the work effort. This coupling and cohesion comes from the systems architecture world is has been shown to increase the robustness of systems. The project cost, schedule, and resulting deliverables are a system, subject to these coupling and cohesion.
The mechanics of the Integrated Master Plan and Integrated Master Schedule looks like this