A Process for Creating and Maintaining Reliable Schedules
As we noted earlier, the best practices described in this guide are presented in no particular order. However, they can be mapped to an overall process of established methods that result in high-quality schedules. This process is presented in figure 1 and described in detail in table 1.
The process in figure 1 is cyclic and described by elaboration through the rolling wave process. As the program proceeds, more becomes known about the detail work that needs to be done; risks are discovered, mitigated, or realized; and effort may be added or reduced.
Figure 1: A Process for Creating and Maintaining Reliable Schedules
Tip: Click the figure to view a larger version in a new browser tab.
Table 1: A Process for Creating and Maintaining Reliable Schedules
Scroll to the right to view full table.
| Process step | Description | Corresponding scheduling best practice |
|---|---|---|
| Capture all activities | Using the work breakdown structure as a basis, all activities are captured in the schedule, including all work necessary by the owner and contractors. The schedule should reflect all effort necessary to accomplish the deliverables described in the WBS. Depending on how much is known, some sets of activities will be scheduled in detail and others will be planned in long-duration planning packages. | Capture all activities |
| Create logically sequenced activity network | Activities are listed in the order they are to be performed and are joined with logic to create predecessors and successors. Logic relationships are not made overly complex and date constraints and lags are minimized. | Sequence all activities |
| Estimate work and durations and assign resources | In accordance with rolling wave planning, estimates of work, duration, and effort are created for activities and resources are assigned. Budgets for direct labor, travel, equipment, material, and the like are assigned to both detail activities and planning packages so that total costs to complete the program are identified. | Assign resources to all activities; establish the duration of all activities |
| Validate critical path and reasonable total float |
The critical and longest paths are identified and validated by the schedulers, management, and subject matter experts. Estimates of total float are examined for reasonableness and extreme values of float are confirmed after validating the network logic. Date constraints causing negative total float are examined and justified. The initial plan or updated schedule may need to be optimized. Strategies for recovery and acceleration can be used to allocate resources more efficiently and to meet time or cost constraints. Recovery options are created for significant forecasted delays. |
Confirm that the critical path is valid; ensure reasonable total float |
| Analyze schedule risk |
Data about program schedule risks are incorporated into a statistical simulation to predict the level of confidence in meeting a program<92>s completion date; determine the contingency, or reserve of time, needed for a level of confidence; and identify high-priority risks and their mitigation plans. A schedule risk analysis is performed on the schedule before a baseline is set and periodically as the schedule is updated to reflect actual progress on activity durations and sequences. |
Conduct a schedule risk analysis; capture all activities |
| Verify and validate traceability | The schedule<92>s traceability, horizontally and vertically, is verified. Horizontal traceability ensures that products and outcomes are linked to associated activities. Vertical traceability ensures that data are consistent between different levels of the schedule. | Verify that the schedule can be traced horizontally and vertically |
| Set and document baseline | The baseline schedule is designated the target schedule and is subjected to configuration management control. A corresponding basis document explains the overall approach to the program and documents and justifies features of the schedule. | Maintain a baseline schedule |
| Update, revise, and manage change |
Progress updates and logic provide a realistic forecast of start and completion dates for activities. The true status of the program is reflected through the integrity of the schedule logic. Performance is measured, monitored, and reported against the baseline schedule. The schedule is monitored to reveal when forecasted completion dates differ from baseline dates and whether schedule variances will affect downstream work. Trend analysis provides insight into program performance. Strategies for recovery and acceleration can be used to allocate resources more efficiently and to meet time or cost constraints. Recovery options are created for significant forecasted delays. |
Update the schedule using actual progress and logic; maintain a baseline schedule |
Source: GAO and Keith D. Hornbacher | GAO-16-89G
The remainder of this document consists of detailed definitions and descriptions of the ten best practices.