Network diagram

The network diagram is a visual display of the relationship between schedule elements. The purpose is to visually depict the types of relationships between components. The components are shown nodes that are connected by lines with arrows that indicate the nature of the relationship. Relationships can be one of four types:

  1. Finish-to-start (FS). This is the most common type of The predecessor element must be complete before the successor element can begin.
  2. Start-to-start (SS). In this relationship, the predecessor element must begin before the successor element
  3. Finish-to-finish (FF). In this relationship, the predecessor element must be complete before the suc- cessor element can be
  4. Start-to-finish (SF). This is the least common type of The successor element must begin before the predecessor element can be complete.

In addition to the types of relationships, the network diagram may show modifications to the relation- ships, such as leads or lags:

  • A lag is a directed delay between In a finish-to-start relationship with a three-day lag, the successor activity would not start until three days after the predecessor was complete. This would be shown as FS+3d. Lag is not float.
  • A lead is an acceleration between elements. In a finish-to-start relationship with a three-day lead, the successor activity would begin three days before the predecessor was This would be shown as FS–3d.
  • Leads and lags can be applied to any type of relationship.

The network diagram can receive information from:

  • Assumption log
  • Schedule management plan
  • Activity list
  • Activity attributes
  • Milestone list
  • Scope baseline

It provides information to:

  • Project schedule

The network diagram is an output from the process 6.3 Sequence Activities in the PMBOK® Guide – Sixth Edition. This is developed once and is not usually changed unless there is a significant scope change.


Tailoring tips

Consider the following tips to help tailor the network diagram to meet your needs:

  • At the start of the project you may want to use sticky notes to create a network diagram to get the idea of the flow of the flow of deliverables.
  • For some projects you will enter the type of relationship directly into the schedule tool rather than draw it Most scheduling software has the option to see the schedule as a network diagram.
  • The network diagram can be produced at the activity level, the deliverable level, or the milestone level.



The network diagram should be aligned and consistent with the following documents:

  • Project schedule
  • Project roadmap
  • Milestone list

Example Network Diagram Form