Logical Relationship
A logical relationship defines how one activity is tied in sequence to another activity or to a milestone, specifying the order and timing of work.
Key Points
- Shows the sequencing link between two activities or between an activity and a milestone.
- Common types include finish-to-start (FS), start-to-start (SS), finish-to-finish (FF), and start-to-finish (SF).
- Leads and lags can be applied to adjust the timing of the relationship.
- Used to build the network diagram and drive the project schedule logic.
Example
The team cannot start system testing until coding is completed (finish-to-start). Also, the "Regulatory Approval Granted" milestone must occur before construction mobilization can begin.
PMP Example Question
Which logical relationship best describes a situation where testing can only begin after development is complete?
- Finish-to-Start (FS)
- Start-to-Start (SS)
- Finish-to-Finish (FF)
- Start-to-Finish (SF)
Correct Answer: A — Finish-to-Start
Explanation: In a finish-to-start relationship, the successor (testing) cannot start until the predecessor (development) finishes.