CFL Guidelines for Developing October 2006
Critical Path Method Schedules (CPMs)
- 26 -
5.4 Terms and Definitions
Activity: Performance of a specific task having a duration.
Bar Chart (Gantt Chart): A schedule format (type) showing activities, sequencing, durations, task
interrelationships and start & finish dates.
Calendar: The scheduling mechanism that determines working time for resources and tasks.
Concurrent Activities: Activities which occur at the same time.
Constraint: Limitations placed on an activity, usually a "must start" or "must finish" date.
CPM: Critical Path Method predicts project duration by analyzing with sequence of activities.
Critical Path: The series of tasks that must be completed on schedule for a project to finish on schedule.
Or, the longest path for the earliest completion having zero (or least) float.
Duration: Time to complete an activity.
Early Start (ES)/Early Finish (EF): The earliest an activity can start or finish on the schedule.
Event: A zero-duration activity.
Finish-to-Finish (FF): Relationship between activities where the finish of the first activity is tied to the
finish of the second activity.
Finish-to-Start (FS): Relationship between activities where the start of the first activity is tied to the
finish of the second activity. (Most common).
Float: The amount of time between the early start and late start of an activity or group of activities.
Free Float (FF): The amount of time an activity can be delayed before it impacts the next activity.
Lag: Time offset between activities.
Late Start (LS)/Late Finish (FS): The latest an activity can start or finish without delaying project
completion.
Logic Loop: Sequence of activities with no end.
Logic: The relationship or "link" between activities or groups of activities.
Milestone: A reference point marking a major event in a project and used to monitor the project's
progress. Any task with zero duration is automatically displayed as a milestone within Microsoft Project.
Negative Float: Total float that is less than zero.
Network: graphical model of the project which shows activities and interrelationships.
Nonworking time: Hours or days designated in a resource or project calendar when Project should not
schedule tasks because work is not done. Nonworking time can include lunch breaks, weekends, and
holidays, for example.
Predecessors: Activities that must precede any given activity.
Pure Logic Diagram: A schedule format (type) showing tasks, sequencing and interrelationships
between tasks.
Start-to-Finish (SF): Relationship between activities where the start of the first activity is tied to the
finish of the second activity.
Start-to-Start (SS): Relationship between activities where the start of the first activity is tied to the start
of the second activity.
Subtask: A task that is part of a summary task. The subtask information is consolidated into the summary
task.
Successors: Activities that must succeed any given activity.
Task: An activity that has a beginning and an end.
Time Logic Network Diagrams (CPM): A schedule format (type) showing activities, sequencing, time-
scaled durations, and task interrelationships with lags, float and start & finish dates.
Total Float (TF): The amount of time an event can be delayed without delaying project completion.