HKSM
Activity-on-Node (AON)
A schedule network technique where each activity is drawn as a node (box) and dependencies are shown with connecting arrows (FS, SS, FF, SF). It is the standard, widely used form of the precedence diagramming method (PDM).
Key Points
- Activities appear as nodes; arrows indicate the direction and type of dependency.
- Supports four relationship types (FS, SS, FF, SF) and allows leads and lags.
- Forms the basis for critical path analysis and schedule compression (crashing, fast-tracking).
- Synonymous with the precedence diagramming method (PDM) used in most scheduling tools.
Example
In a software project, “Design UI” must finish before “Build Frontend” starts (FS). “Configure CI/CD” can begin two days after “Set Up Repositories” starts (SS with a 2-day lag). “System Test” cannot finish until “Integration” finishes (FF). This network is modeled using AON/PDM with boxes for each activity and arrows for the relationships.
PMP Example Question
A scheduler draws boxes for each task and connects them with arrows labeled FS and SS. Which technique is being used?
- Activity-on-Node (AON)
- Activity-on-Arrow (AOA)
- GERT network diagram
- Milestone chart
Correct Answer: A — Activity-on-Node network diagram (PDM)
Explanation: In AON, activities are nodes and arrows show precedence relationships (the PDM approach). AOA represents activities as arrows, not boxes.
