What is Dependency Types (FS, SS, FF, SF)?
Four logical relationships link activities: Finish-to-Start (successor starts after predecessor finishes — 90% of real schedules), Start-to-Start (both may run once the first begins), Finish-to-Finish (successor can't finish until predecessor does), and the rare, brain-bending Start-to-Finish (successor can't finish until predecessor starts — think shift handovers).
Exam approach: identify who's predecessor and successor first, then read the relationship left to right. Most wrong answers come from skipping step one.
Worked example
Pipeline job: trench → lay pipe is FS. Lay pipe and inspect welds run SS (inspection starts once laying starts, then trails along). Backfill and final grading are FF — grading can't finish until the last backfill does. And the night security contract is SF: the old guard service can't finish until the new one starts. All four, one project, and none of them interchangeable.