Schedules are working tools for program planning, evaluation and control.
They are developed in many iterations with project team members and continuing feedback from the client. The quality of a schedule has a major effect on the sources of the project and frequently affects other projects that compete for the same resources. Appropriate level of detail and timing. Every key milestone should represent a checkpoint for a collection of activities at the completion of a major project phase. No two activities can be identified by the same head and tail events.