Introduction to Gantt Charts and Task Networks

Introduction to Gantt Charts and Task Networks

It is time to leave for work. I. M. Late has to eat breakfast and put on shoes & socks. How long will it take? Here’s a task list:

1. Breakfast Bars
2. Left Sock
3. Left Shoe
4. Right Sock
5. Right Shoe
6. Out the Door

Tasks 1 through 5 are Estimated Duration tasks, task 6 is a Milestone.

Here is a Gantt chart view of the task schedule:

What are the durations of the tasks in this view?

There are Finish-to-Start (FS) task dependencies between Tasks 2 and 3 and between tasks 4 and 5. There are Start-to-Finish dependencies between Milestone task 6 and tasks 3 and 5.

Here is a Network view of the same schedule, tasks with dependencies are linked:

A Network view is not a schedule, it shows the sequence of activities from left to right and shows the logical relationships between them

Notice that all the tasks are outlined in red, the default color for Critical Activities, indicating that a delay in any of the tasks will delay the project. You can see from the Gantt Chart that the timely completion of all tasks is critical too, they take up all of the available time. How long is this schedule?

Assuming that our friend Late can chew and put shoes & socks on at the same time, task 1 can overlap tasks 2 through 5.

However, since you can’t put on two socks or two shoes at the same time, there is a resource constraint on shoes & socks, they can not happen simultaneously so I. M. Late decides to do the left first:

How long is the schedule now?

This chart shows the FS dependencies in the Shoes & Socks tasks. Right Sock now has a Finish-to-Start dependency with Left shoe and the Start-to-finish dependency between tasks 6 and 3 is no longer necessary. Notice that task 1, Breakfast Bars now has some slack in it, it can happen at any time, while the Shoes & Socks task is occurring, it