Learning objective
Construct a valid dependency network, perform forward and backward passes and explain why criticality changes with actual progress.
Why it matters
A target date does not explain how work can reach it. Network logic reveals which branch controls the finish, which tasks have float and where a delay actually matters.
Core concept: calculate, then test feasibility
For finish-to-start work, the forward pass uses the maximum predecessor finish at a merge. The backward pass uses the minimum successor start at a branch. Zero total float identifies the current critical path, subject to logic, calendars and constraints.
Scenario
A–B–D takes 9 days; A–C–E takes 11. A scarce engineer is assigned to B and C even though the network shows them in parallel.
Worked decision
The logic-only critical path is A–C–E. The schedule is not yet feasible because B and C contend for one resource. Resolve or model that constraint, then recalculate.
Decision rule
Never report a critical path without the status date, calendar, duration basis, dependency logic and resource/constraint qualification.
AI lens
AI can calculate and compare scenarios, but the people responsible for the work validate dependencies, estimates and compression risk.
Quick check
At a merge point, which predecessor determines earliest start?
A. The one with the earliest finish.
B. The one with the latest earliest finish.
C. The most senior owner.
D. The shortest duration.
Answer: B.
Next step
Build the CPM workspace and solve the data-migration case.