Schedule Maintenance and Control
Baseline, Updates, and Progress
Control requires a stable baseline against which performance is measured. Know the update cycle: collect progress (actual start/finish, remaining duration, percent complete), apply a data date (status date), recalculate, and compare. The data date is the boundary between actuals and forecast; no work should be reported after it. Retained logic vs. progress override is a key distinction: retained logic preserves original sequencing for incomplete work, while progress override allows out-of-sequence work to proceed without preserving all logic.
Percent Complete Methods
Duration-based, units-based, and physical percent complete differ. Earned value integrates schedule and cost: PV, EV, AC; SV = EV − PV; SPI = EV ÷ PV; CV = EV − AC; CPI = EV ÷ AC. SPI below 1.0 means behind schedule in cost terms, not necessarily time.
Change Control
Schedule changes flow through change control: identify, evaluate impact, approve/reject, and re-baseline only with authorization. Know that re-baselining resets performance measurement and must be documented.
Worked Example
At the data date, PV = 100, EV = 80, AC = 90. SV = −20 (behind), SPI = 0.80, CV = −10, CPI = 0.89. Forecast: EAC = BAC ÷ CPI.
Traps
Confusing data date with update date; treating percent complete as linear when it is not; and forgetting that out-of-sequence progress can create false float. Always verify logic before trusting float values after an update.