PMI started in 1969 with a conference and a white paper and has grown to publish the 6th edition of its standard, the “Project Management Body of Knowledge guide” commonly called the PMBOK. The PMI system divides the 49 identified processes related to projects into a matrix of 5 process groups by 10 knowledge areas. See table 1-4 in the PMBOK. The processes interact with one another in a Plan, Do, Check, Act, iterative manner as they progress from project initiation to closure. The PMBOK also contains a rich collection of tools, concepts, and nuances that influence the use of process input and results of the outputs. Not all 49 processes are applied to every project, but every process should be given consideration. A fundamental principle of PMI is to do what is necessary.
Project Management also uses a principle called Progressive Elaboration to deal with early project information deficiencies. It basically says, don’t be paralyzed by it; plan, and then improve the plan iteratively, as more information becomes apparent and available. The PMI way is Planning, Direction, Adjusting, and Controlling in a fluid and flexible non rigid manner tailored to the customers’ needs. Dwight Eisenhower once said “In preparing for battle I have always found plans to be useless, but the planning to be indispensible.”