A few months ago, a colleague expressed concern to me that when a tasks duration was reduced, the start and finish dates for subsequent tasks weren’t reflecting the change.
Figure 1: Here’s where we were…
When the duration of the “Plan” task was reduced to one day, the “Build” task was still reflecting the old start date. Why?
Figure 2: …but when we reduced Plan by a day, Build didn’t shift.
To validate the completeness of the schedule, I asked three questions about the schedule:
1. Is the project schedule set up from project start date or project finish date? To find out, I opened the “Project Information” dialog box (Project | Project Information) and found that the project was scheduled from “Project Start date.” This was critical to know. If a project is scheduled from “Project Finish date,” then by default all the tasks would be scheduled “As late as possible.”
Figure 3: Scheduling from project Start date.
2. Are the tasks properly linked to each other? I viewed the network diagram of the schedule (View | Network diagram) and found it was closed. The right critical path would be identified by project only if the dependencies between tasks were logical.
Figure 4: A view of the links between tasks.
3. Are there any schedule constraints attached to the task? I checked out “Indicators” to find any constraints. Bingo! The task information for “Build” indicated a “Start No Earlier Than” constraint, which was set, preventing the task from starting earlier.
Figure 5: The Indictators column provides clues about schedule constraints.
Figure 6: A drill down on that task divulged the constraint.
To solve the problem, I changed the “Constraint type” of “Build” task to “As Soon As Possible” and then checked to see if the schedule was now flexible. Yes, it was!
Figure 7: Problem remedied.
Lessons Learned
I can extrapolate the solution provided in general to the following principles:
- Create a unique deliverable. Each task should create a verifiable, tangible deliverable.
- Set up a closed network diagram. All the tasks in a schedule expect the first and last task to have at least one predecessor and successor.
- Minimize date constraints. Add date constraint (Start-No-*, Finish-No-*) to a task only if it is dependent on a non-project activity outside the control of the project management team, such as approval of government order or software installation by vendor.
