Network diagram
A network diagram is a project management practice to develop the project schedule. With this practice is possible to see project activities sequence and their dependencies, and as a consequence the logical order of the project. The network diagram can also have the activity duration, restrictions, and milestones, giving the full vision of the project.
Benefits of using a network diagram in project management
The main advantage of the network diagram is to give the full perspective of the logical order of the activities necessary to complete the project. This way, the project manager can see the full picture of all activities that the team needs to complete, in the right order. Plus, adding activity duration gives the team the idea of when each activity will be completed as well as the project, a phase, a deliverable, and so on.
After the project manager determines the project duration, he knows which activities are on the critical path, doesn’t have slack, and cannot delay. In other words, the project manager learns what activities cannot delay without delaying the project or an important deadline. He also learns which activities can delay, and how long, so we can move resources from those activities to the ones on the critical path, if necessary.
The network diagram also allows the project manager to find opportunities to compress the schedule and reduce the total duration of the project. The project manager can do this by parallelizing activities and moving resources from non-critical activities to critical activities.
The network diagram is also a powerful tool during the execution of the project to monitor and control the progress of the project. Like this, the project manager can compare the actual performance with the planned performance and learn if the project is in the right way or not.
Benefits for other stakeholders involved in the project
Until now we only talked about the advantages to the project manager, but the network diagram is also very useful for the stakeholders. Since is a graphical representation of the project, the stakeholders can have a visual idea of the project’s progress. They can also have an idea of how the work is flowing. Additionally, the team can also have this visual perspective of the project’s progress and the flow. Indeed, the network diagram is also a good communication tool for everybody involved in the project.
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Different types of network diagram
The project team can develop the network diagram using 2 conventions. Both have their advantages and disadvantages. Let’s see each other in more detail.
Precedence diagram method (PDM)
The most common convention to represent the network diagram is the Precedence Diagramming Method (PDM) or activity on Node. The project team can create the network diagram using this method by representing the activities in boxes or nodes. Then they can connect lines between the boxes or nodes to represent the sequences. Next to each box, the team can register additional information like duration, the slack, or the float. Having the relationship between activities represented with arrows allows great flexibility since it is possible to represent multiple dependencies. Like that, the team can represent the following dependencies:
- Finish to start – An activity can only start if another ends
- Start to start – An activity can only start if another activity starts
- Finish to finish – An activity can only finish if another finishes
- Start to finish – An activity can only finish if another starts
Arrow Diagramming Method (ADM)
The other convention to represent the network diagram is the Arrow Diagramming Method (ADM) or Activity on Arrow (AOA). The team when using this convention represents the activities on arrows or lines and the dependencies on boxes or nodes. This method is losing relevance because is very limited. This method just allowed the representation of “finish-to-start” dependencies. To be able to represent other types of dependencies you must create “dummy” activities.