The Change Process
The baseline and current schedules should be subjected to a change control process. A control process governs when and how technical and programmatic changes are applied to the baseline, as well as the content of the current IMS. A proper change control process helps ensure that the baseline and current schedule are accurate and reliable. Without a documented, consistently applied schedule change control process, program staff might continually revise the schedule to match performance, hindering management’s insight into the true performance of the project. Undocumented or unapproved changes hamper performance measurement and may result in inaccurate variance reporting, inconsistent stakeholder versions of the plan, and unreliable schedule data. Moreover, if changes are not controlled and fully documented, performance cannot be accurately measured against the original plan.
Program management decides on the extent to which the IMS is subjected to a change control process; it depends on the program size, scope, risk, and complexity. Less complex projects may subject only key milestones or high-level WBS activities to the change control process, so that changes to supporting detailed activities do not require change approval. For more complex and tightly controlled schedules, lower-level detail activities as well as network dependencies may also be subjected to change approval.
The current schedule, once management approves it, should be assigned a version number and archived. This ensures that all status updates can be traced and it guarantees that all stakeholders are using the same version of the current schedule. Case study 19 highlights a complex, highly detailed schedule that was successfully updated regularly according to a defined process.
For the 2010 Decennial Census schedule, the U.S. Census Bureau had implemented processes around its master schedule that complied with a number of scheduling process criteria that are important to maintaining a schedule that is a useful management tool. The Bureau ensured that the schedule would be complete with input from stakeholders throughout the agency, with reviews of previous schedules that built on a number of census tests during the decade. As a result, the schedule was the primary source senior managers used to determine weekly what census activity was ahead of or behind schedule, and it provided a resource for determining the effects on the overall project of any delays in major activities.
The Bureau had documented and implemented a formal process for keeping the data in the schedule current. Staff within each Bureau division were responsible for ensuring that the status of schedule activities was updated weekly. Staff updated the actual start and finish dates, the percentage of each activity completed so far, and estimates of the time remaining to complete each activity in progress. The Bureau was recording status information on an average of more than 1,300 activities in the schedule during any given week, generating historical data that could provide valuable input to future schedule estimates.
In addition, the Bureau implemented a formal change control process that preserved a baseline of the schedule so that progress could be meaningfully measured. The Bureau’s criteria for justifying changes were clearly documented, approval for them was required by a team of senior managers, and each team acknowledged their effect within the Bureau. About 300 changes had been approved since the master schedule was baselined in May 2008. Even corrections to the schedule for known errors, such as incorrect links between activities, had to be approved through the change control process, helping to ensure the integrity of the schedule.Changes to the baseline schedule should be limited to revisions for new or reduced scope or for formal replanning. At times, however, management may conclude that the remaining schedule target for completing a program is significantly insufficient and that the current baseline is no longer valid for realistic performance measurement. The purpose of schedule rebaselining is to restore management’s control of the remaining effort by providing a meaningful basis for performance management.
Working to an unrealistic baseline could worsen an unfavorable schedule’s condition. For example, if variances become too big, they may obscure management’s ability to discover newer problems that could still be resolved. To quickly identify new variances, a schedule rebaseline normally eliminates historical variances. A rebaselined schedule should be rare. If a program is rebaselined often, it may be that the scope is not well understood or simply that program management lacks effective discipline and is unable to develop realistic estimates.