AACE PSP key terms

A hierarchical decomposition of the total scope of work into manageable, deliverable-oriented components. It provides the framework for defining activities, assigning responsibility, and rolling up cost and schedule data for reporting.

A distinct, definable unit of work performed during a project that consumes time and usually resources. Activities are the building blocks of a schedule network and are assigned durations, logic ties, and progress status.

The number of work periods, expressed in calendar or working units, required to complete an activity or project phase. Duration differs from elapsed time when non-working periods such as weekends or holidays intervene.

A dependency linking two activities that constrains when the successor may start or finish relative to the predecessor. Common types include finish-to-start, start-to-start, finish-to-finish, and start-to-finish, each optionally carrying a lag.

A deliberate, positive time interval inserted between the finish or start of a predecessor and the start or finish of its successor. Lag models waiting periods such as cure time or approval delays within the logic network.

A negative time interval applied to a logic relationship that allows a successor to begin or finish before its predecessor reaches the linked milestone. Lead accelerates work but can create unintended schedule compression risk.

A graphical representation of activities and their logical relationships, typically drawn as nodes connected by arrows. It forms the model from which forward and backward passes calculate early and late dates.

A deterministic scheduling technique that calculates early and late dates through forward and backward passes, identifying the longest path through the network. Activities on that path have zero or minimum total float and drive project completion.

A calculation that moves from project start to finish, assigning each activity its earliest possible start and finish based on predecessor logic and durations. It establishes the shortest achievable project duration given the network.

A calculation that moves from project finish back to start, assigning each activity its latest permissible start and finish without delaying the project. Comparing late dates to early dates yields total float.

The amount of time an activity can be delayed from its early start without delaying the project finish date. Total float is shared along a path and is computed as late finish minus early finish or late start minus early start.

The amount of time an activity can be delayed without delaying the early start of any immediate successor. Unlike total float, free float belongs to a single activity and is not shared with downstream work.

The approved, time-fixed version of the project schedule against which actual progress and performance are measured. Changes to it require formal change control and a reissued baseline for variance analysis.

A scheduling technique that adjusts activity start and finish dates to resolve resource over-allocation or to smooth demand within imposed limits. Leveling may extend the project duration and alter the critical path.

A technique that shifts activities within their available float to reduce peaks and valleys in resource demand without changing the project finish date. Unlike leveling, smoothing never extends the critical path.

A set of techniques applied to shorten the schedule without reducing scope, chiefly crashing and fast tracking. Compression typically raises cost, risk, or both and must be evaluated against project objectives.

A schedule compression technique that shortens duration by adding resources or working overtime, usually at increased cost. It targets critical-path activities where the cost per unit of time saved is lowest.

A schedule compression technique that overlaps activities normally performed in sequence, often by converting finish-to-start logic to start-to-start with lag. It shortens duration but increases rework and coordination risk.

A defined pattern of working and non-working periods that governs how durations convert into dates. Project, resource, and activity calendars interact, and mismatches between them are a frequent source of schedule error.

A significant point or event in the project with zero duration, used to mark completion of a phase, delivery of a deliverable, or a contractual obligation. Milestones carry no work but anchor reporting and payment triggers.

The routine process of updating the schedule model with actual dates, remaining durations, and revised logic to keep it a valid representation of the plan. It includes status updates, data checks, and reissuing controlled versions.

A measure of work accomplished on an activity or project, expressed as a proportion of the total. It may be based on duration, physical units, or cost and must be paired with remaining duration for accurate forecasting.

The estimated work periods still needed to finish an activity from the status date, independent of time already spent. Correct remaining durations, not percent complete alone, drive reliable forecast dates in an updated schedule.

The point in time at which schedule progress is recorded and the schedule is updated, also called the status date. Work after the data date is forecast; work before it is historical and should reflect actuals.

A condition where actual execution violates the planned logic, such as a successor starting before its predecessor finishes. It can distort float and critical path calculations unless the logic is corrected or progress is properly retained.

An integrated performance method comparing planned value, earned value, and actual cost to measure scope, schedule, and cost performance. Schedule performance indicators derived from EVM complement network-based schedule analysis.

A performance measure of schedule achievement, typically earned value minus planned value in cost terms. A negative value indicates work is behind plan; it signals schedule slippage but not necessarily delay to the finish date.

The ratio of earned value to planned value, indicating how efficiently schedule work is being accomplished. Values below one signal slower-than-planned progress; SPI trends support forecasting of completion dates.

The projected completion date of an activity or the project derived from current progress, remaining durations, and logic. It is compared with the baseline finish to quantify expected delay and support recovery planning.

A short-interval, rolling extract of upcoming work, often covering two to six weeks, used to coordinate crews and identify constraints. It translates the master schedule into actionable near-term commitments for field execution.

A formal process for submitting, evaluating, approving, and documenting modifications to the schedule baseline or project plan. Approved changes are incorporated into a revised baseline so that performance comparisons remain meaningful.

The integrated, time-phased scope, schedule, and cost baseline against which project execution is measured. It comprises the schedule baseline plus budgeted cost and is the reference for earned value analysis.

The reduction of available total or free float as activities slip or are resequenced during updates. Tracking float consumption reveals eroding schedule flexibility and warns of emerging criticality before dates actually slip.

The longest continuous chain of dependent activities through the network, which determines the shortest possible project duration. Any delay on this path delays project completion unless float or logic is adjusted.

A path whose total float is very small, often defined by a threshold such as less than a reporting period. Monitoring near-critical paths provides early warning of activities likely to become critical after minor slippage.

A quantitative method, often using Monte Carlo simulation, that models uncertainty in durations and logic to produce probabilistic completion dates. It identifies activities with high sensitivity and informs contingency reserves.

A management point within the WBS where scope, schedule, and cost are integrated and performance is measured. Control accounts align schedule activities with budgets and are the building blocks of earned value reporting.