The objective of the project plan is to define the project in detail and to provide a baseline against which to compare progress . The project plan document is the main project document for managing the project and contains time, cost, scope and quality information for the project.
A Project without a plan is not considered to be a project. The creation of the project plan is a major milestone of the project and is the most important document which will be produced during the project lifetime. The project plan document will be used through out the dictation of the project to monitor the activities of the project. The project plan should include input from everybody involved with the project.
The complexity of the project will dictate to a large extent the timeframe for the creation of the project plan. It may not be possible to create a complete project document at the start. Complex projects are divided in phases, each with a plan of its own. Complex work packages may also require a work package plan of their own. The overall project plan will be the summation of all the work package plans and the phase plans.
The project plan is reviewed continually, to ensure that the project work is taking place according to the project plan. It is rare for the project plan to accurately describe every element of the project. The project is a dynamic environment, where the requirements can easily change what seemed to be a reasonable goal a few months ago may appear to be a pipe dream at present and vice versa. All projects require some sort of change to the project plan document during the course of the project.
If there is significant deviation from what is stated in the project plan, phase plan or work package plan, then the plan needs to be amended, through a change order. In the case of a serious deviation, there may be a need to replace the existing plan with a new plan of equal complexity.