Glossary of Construction Scheduling Terms

Activity

A task or process completed within a set timeframe as part of a larger project. Activities can be assigned to resources, have associated costs, and are linked logically to form a schedule.

Activity Code

An alphanumeric identifier used to group and filter activities. Each activity is assigned a code for categorization and reporting.

Activity Relationship

A logical connection between two activities, defining their sequence. The four relationship types are:

FS (Finish-to-Start) – Successor cannot start until predecessor finishes.

SS (Start-to-Start) – Successor cannot start until predecessor starts.

FF (Finish-to-Finish) – Successor cannot finish until predecessor finishes.

SF (Start-to-Finish) – Successor cannot finish until predecessor starts.

Baseline Schedule

A fixed CPM schedule representing the original project scope and intended work sequence. Used as a benchmark for measuring schedule performance.

Constraint

A date restriction placed on an activity’s start or finish date, overriding system-calculated dates. Often used to impose deadlines or intentional delays.

Contract Completion Date

The date defined in the contract by which all project work must be completed.

Critical Activity

An activity on the critical path with zero float; any delay will directly impact project completion.

Critical Path

The longest sequence of dependent activities through the schedule with the least float, determining the earliest possible project completion date. It may shift during execution due to progress or changes.

Current Schedule

The latest officially approved version of the project schedule.

Data Date (As-of Date)

The cut-off point in time where actual progress is recorded, separating actual data from planned future activities.

Duration

The total calendar time needed to complete an activity, from start to finish.

Finish-to-Start (FS)

A common logic relationship where a successor begins only after the predecessor finishes.

Finish-to-Finish (FF)

A successor cannot finish until the predecessor finishes.

Float

A successor cannot finish until the predecessor finishes.

Fragnet

A subset of activities within the schedule, typically representing a specific event like a delay or change.

Gantt Chart

A visual time-based chart showing scheduled activity durations as horizontal bars, often used in reporting and progress tracking.

Impacted Schedule

A CPM schedule revised to reflect pending changes, delays, or contract modifications that may alter the critical path.

Interim Completion Date

A milestone date in the contract requiring partial project completion before full completion.

Interim Project Schedule

A short-term schedule (usually the first 90 days) showing initial planning and later integrated into the full baseline schedule.

Lag

A defined delay between predecessor and successor activities in a logic link.

Master Schedule

A comprehensive CPM schedule that consolidates multiple related projects or work packages for unified tracking.

Milestone

A zero-duration event marking a significant point in the project timeline. Used for reference and summary reporting.

Near-Critical Activity

An activity with low float that is at risk of becoming critical if delayed. Defined based on project-specific thresholds.

Negative Lag (Lead)

A time overlap allowing a successor to begin before a predecessor finishes, accelerating the schedule.

Positive Lag (Lag)

A delay assigned between activities to postpone the start of a successor.

Predecessor

An activity that must occur before another begins or ends, based on defined relationships.

Project Scheduler

A skilled professional responsible for planning, developing, and maintaining CPM schedules. Liaises with contractors and owners to assess schedule progress and updates.

Recovery Plan

A revised CPM schedule outlining strategies to bring the project back on track following delays or performance issues.

Revised Schedule

A newly developed schedule reflecting significant changes or impacts affecting the project trajectory.

Scheduled Completion Date

The projected finish date of all work as shown in the current CPM schedule.

Start-to-Finish (SF)

A successor activity finishes only after the predecessor starts.

Start-to-Start (SS)

A successor activity starts only after the predecessor starts.

Successor

An activity that follows and is dependent on another activity based on logic ties.

Total Float

The maximum time an activity can be delayed without affecting the project’s overall finish date.

Unimpacted Schedule

The latest approved schedule version before a delay or issue arose, often used as a reference for impact analysis.

Update Schedule

An updated CPM schedule reflecting actual progress from the previous data date to the current one.

Work Breakdown Structure (WBS)

A hierarchical decomposition of the project into phases, deliverables, and tasks. WBS organizes work for better planning and control.