The Project Schedule Part 5: Dependencies

Planning

Now that you have your lowest level scheduled tasks defined and have assigned resources, it is time to define the dependencies between tasks. This is where MS Project really comes in handy as it will create the schedule for you based on task dependencies and resource availability.

There are four types of dependencies:

  • Finish to Start – This is the most common and the default in MS Project. The predecessor must finish before the successor can start. For example, “Applying Primer” must finish before “Painting” can start.
  • Start to Start – Predecessor must start before the successor can start. For example “Mortgage Application” must start before “Credit Check”.
  • Finish to Finish – Predecessor must finish before the successor can finish. This can be true of tasks that run in parallel but both are needed for the subsequent task.
  • Start to Finish – Predecessor must start before the Successor can finish. This one is rarely used and frankly should be avoided.

When you initially define the dependencies, take care to only define “true” dependencies. If you have one person assigned to all the tasks you may be tempted to make all of the tasks dependent since the resource must complete one before starting another. Don’t do this. Let MS Project do this via resource leveling. The reason for not doing this is you may get additional resources later so some tasks can run in parallel. If you made them all dependent, the schedule will not show this possibility.

MS Project can now take your tasks, resource assignments, estimates and dependencies and create an initial schedule. I say initial because you often will find with your first cut that the finish date does not occur within the Sponsor’s expected time frame. In the next topic I will discuss the concept of the “Critical Path” and what the Project Manager can do to rein in the target date.

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