Create a Network Diagram of Your Work Plan

Planning and organizing is time well spent when managing a project. A network diagram is a flowchart that illustrates the order in which you plan to perform project activities. No matter how complex your project is, its network diagram has the following three elements: milestones, activities, and durations.

  • Milestone: Milestones take no time and consume no resources; they occur instantaneously. Think of them as signposts that signify a point in your trip to project completion. Milestones mark the start or end of one or more activities.

  • Activity: An activity is a component of work performed during the course of a project. Activities take time and consume resources; you describe them using action verbs. Examples of activities are design report and conduct survey.

    Make sure you define activities and milestones clearly. The more clearly you define them, the more accurately you can estimate the time and resources needed to perform them, the more easily you can assign them to someone else, and the more meaningful your reporting of schedule progress becomes.

  • Duration: This represents the total number of work periods it takes to complete an activity. The amount of work effort required to complete the activity, people’s availability, and whether people can work on the activity at the same time all affect the activity’s duration.

    Understanding the basis of a duration estimate helps you figure out ways to reduce it. For example, suppose you estimate that testing a software package requires that it run for 24 hours on a computer. If you can use the computer only 6 hours in any one day, the duration for your software test is four days. Doubling the number of people working on the test won’t reduce the duration to two days, but getting approval to use the computer for 12 hours a day will.

Determining your project’s end date requires you to choose the dates that each project activity starts and ends and the dates that each milestone is reached. You can determine these dates with the help of a network diagram.

The activity-on-node technique for drawing a network diagram uses the following three symbols to describe the diagram’s three elements:

  • Boxes: Boxes represent activities and milestones. If the duration is 0, it’s a milestone; if it’s greater than 0, it’s an activity. Note that milestone boxes are sometimes highlighted with lines that are bold, double, or otherwise more noticeable.

  • Letter t: The letter t represents duration.

  • Arrows: Arrows represent the direction work flows from one activity or milestone to the next. Upon completion of an activity or reaching of a milestone, you can proceed either to a milestone or directly to another activity as indicated by the arrow(s) leaving that activity or milestone.

In this simple example of an activity-on-node network diagram, when you reach Milestone A (the box on the left), you can perform Activity 1 (the box in the middle), which you estimated will take two weeks to complete. Upon completing Activity 1, you reach Milestone B (the box on the right). The arrows indicate the direction of workflow.