AACE CST key terms

A hierarchical breakdown 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 information for reporting.

A discrete, identifiable unit of work performed during a project that has a defined start, finish, duration, and resource requirements. Activities form the building blocks of a schedule network and are progress measured.

The longest continuous sequence of dependent activities through a network, determining the shortest possible project duration. Activities on this path have zero or minimum total float and drive the project completion date.

The amount of time an activity can be delayed from its early start without delaying the project finish date or a constrained milestone. It equals late finish minus early finish, or late start minus early start.

The time an activity can slip without delaying the early start of any immediate successor. It is the difference between the successor's early start and the activity's early finish, minus any lag.

A dependency connecting two activities that defines the sequence in which they can be performed. Relationships may be mandatory, discretionary, or external and are expressed as finish-to-start, start-to-start, and similar types.

A logical relationship in which a successor activity cannot begin until its predecessor finishes. It is the most common dependency type in construction and engineering schedules and may include a lag.

A planned, positive waiting period inserted between the finish of a predecessor and the start of its successor, or between other relationship points. Lag models real constraints such as curing time or approval delays.

A negative lag that allows a successor activity to begin before its predecessor finishes or advances the relationship by a specified time. Leads should be used sparingly because they can obscure true dependencies.

A schedule event with zero duration marking a significant point, such as completion of a phase, contractual delivery, or a key decision. Milestones are used for high-level tracking and executive reporting.

The total number of work periods, usually expressed in days or weeks, required to complete an activity from start to finish. Duration excludes nonworking time and depends on resources, productivity, and calendar.

A defined set of working and nonworking days and hours used to schedule activities. Project and resource calendars determine when work can occur and directly affect calculated dates and durations.

An approved, time-phased plan of activities and milestones used as the reference for measuring progress and performance. Changes to the baseline require formal change control and are typically versioned.

The point in time at which schedule status is recorded and progress is measured, also called the status date. Work performed after the data date is considered future work in the update.

A periodic revision of the project schedule that incorporates actual progress, revised durations, logic changes, and remaining work as of the data date. Updates produce a current forecast while preserving the baseline for comparison.

A measure of work accomplished on an activity or project, expressed as a proportion of the total planned scope. It may be based on duration, physical quantities, or earned value, depending on the measurement method.

The difference between earned value and planned value, showing whether schedule work is ahead of or behind plan in cost terms. A negative value indicates less work was accomplished than planned.

A ratio of earned value to planned value that measures schedule efficiency. Values below one indicate work is progressing slower than planned; values above one indicate faster-than-planned progress.

A project control technique that integrates scope, schedule, and cost by comparing planned value, earned value, and actual cost. It provides objective indicators of performance and forecasts likely outcomes.

The authorized budget assigned to scheduled work for a given period. It represents what the project should have earned by a specific point in time according to the baseline.

The value of work actually performed, measured against the approved budget for that work. It converts physical progress into a cost figure and serves as the basis for performance metrics.

The total cost incurred for work performed during a given period. It includes direct and indirect costs and is compared with earned value to assess cost performance.

The sum of all authorized budgets for the project scope, representing the total planned cost baseline. BAC is used as the denominator for cost and schedule performance indices and as a reference for forecasts.

A forecast of the total cost expected to complete all project work, based on actual performance and remaining work. Common formulas divide budget at completion by cost performance index or add estimates to complete.

A scheduling technique that adjusts activity start and finish dates to resolve resource over-allocation or shortages. It may extend the project duration and often changes the critical path and float values.

A technique that shifts activities within their available float to reduce resource demand peaks without extending the project completion date. Unlike leveling, it cannot delay the critical path.

A restriction placed on an activity's start or finish date, such as start-no-earlier-than or finish-no-later-than. Constraints override network logic and can consume float or alter the critical path.

A scheduling method that calculates early and late dates for activities by analyzing network logic and durations. It identifies the critical path and float, enabling systematic planning and control of project time.

A graphical representation of activities and their logical relationships, showing the sequence of work and dependencies. It is used to visualize the schedule, trace paths, and identify the critical path.

An estimating technique that uses optimistic, most likely, and pessimistic durations to calculate an expected value and range. It helps account for uncertainty in activity durations and supports schedule risk analysis.

A progressive planning approach in which near-term work is detailed while future work is planned at a higher level. As the project advances, detailed schedules are developed for upcoming phases.

A quantitative or qualitative process that assesses how uncertainties and risks may affect schedule durations and completion dates. Techniques include Monte Carlo simulation, sensitivity analysis, and contingency determination.

A technique used to shorten the project schedule without reducing scope, typically through crashing or fast tracking. It is applied when deadlines are at risk and often increases cost or risk.

A schedule compression technique that shortens activity durations by adding resources or working overtime, usually increasing cost. It targets critical path activities and requires analysis of cost versus time savings.

A compression technique that overlaps activities normally performed in sequence, such as starting design before construction finishes. It can shorten duration but increases risk and rework potential.

A formal process for reviewing, approving, and documenting modifications to the approved baseline schedule or budget. It ensures changes are justified, traceable, and communicated to stakeholders.

The periodic communication of schedule status, accomplishments, variances, and forecasts to stakeholders. Reports typically compare actual progress against the baseline and highlight issues requiring management attention.

A measurable value that shows how effectively a project is achieving key schedule or cost objectives. KPIs are tracked over time to support decisions and compare performance against targets.