When the original plan is agreed to, the Baseline or Target is set. The Baseline is a copy of the original plan and is used to compare progress of an updated schedule. Earlier versions were limited 50 baselines but this restriction has been removed in later versions.
After project planning has ended and project execution has begun, the actual progress is monitored, recorded and compared to the Baseline dates.
The progress is then reported and evaluated against the Baseline.
The plan may be changed by adding or deleting activities and adjusting Remaining Durations, Logic or Resources. A revised plan is then published as progress continues. A revised Baseline may be set if the original Baseline becomes irrelevant due to the impact of project scope changes, a change in methodology or excessive delays.
Updating a schedule assists in the management of a project by recording and displaying:
- Progress and the impact of project scope changes and delays as the project progresses,
- The revised completion date and final forecast of costs for the project,
- Historical data that may be used to support extension of time claims and dispute resolution, and
- Historical data that may be used in future projects of a similar nature.
Projects are often planned at a summary level and then at a later date detailed out before the work commences. Smaller projects may be scheduled in detail during project planning, but large or complex projects may require several iterations before the project plan is fully detailed out.
The main reasons for not detailing out a project early are that:
- There may not be enough information at that stage and
- Preparing detailed schedules wastes time, as they may be made redundant by unforeseen changes.