Developing the Project Schedule
Another characteristic of using the precedence diagramming method are the relationships between activities. There are four relationship types that you can use to “link” activities together; in all of these relationships the first verb describes the predecessor activity and the second verb describes the successor activities. You can see these four relationships in Figure 1.
Here’s their explanation:
- Finish-to-start – Activity A must finish before Activity B can start. Example: The walls must be primed before the walls can be painted. This is the most common relationship you’ll use in project management.
- Start-to-start – Activity C must start before Activity D can start. You’ll use this relationship type when you want two activities to both start at the same time. Example: The network cable installation activity must start so that the network patch panel can be installed. Both activities can happen at the same time.
- Finish-to-finish – Activity E must finish so that Activity F can finish. You’ll use this relationship type when you want, surprise, surprise, both activities to finish at approximately the same time. Example: The software installation activity must finish so the software training class can finish. Users in the software training class will return to their desktops to find the software they’ve just been trained on is now installed on their computer.
- Start-to-Finish– Activity H must start so that Activity G can finish. This is the most unusual and least used relationship type. This relationship is primarily used with just-in-time manufacturing, just-in-time scheduling, and inventory management systems. There often isn’t a real relationship between these activities, but more of a conditional relationship based on scenarios in the project. Example: We need to order more materials when we use the existing materials on the shop floor. We won’t use the existing materials until we have a demand to use the materials – and then we’ll order more to maintain a uniform amount of materials in the shop at all time.
You can find more information about activity relationships and project scheduling here.
