Critical Activity. Any activity on a critical path. Most commonly determined by using the criti-
cal path method. Although some activities are “critical” in the dictionary sense with-
out being on the critical path, this meaning is seldom used in the project context.
Critical Path. In a project network diagram, the series of activities which determines the earli-
est completion of the project. The critical path will generally change from time to
time as activities are completed ahead of or behind schedule. Although normally
calculated for the entire project, the critical path can also be determined for a mile-
stone or subproject. The critical path is usually defined as those activities with float
less than or equal to a specified value, often zero. See critical path method.
Critical Path Method (CPM). A network analysis technique used to predict project duration by
analyzing which sequence of activities (which path) has the least amount of sched-
uling flexibility (the least amount of float). Early dates are calculated by means of a
forward pass using a specified start date. Late dates are calculated by means of a
backward pass starting from a specified completion date (usually the forward pass’s
calculated project early finish date).
Current Finish Date. The current estimate of the point in time when an activity will be completed.
Current Start Date. The current estimate of the point in time when an activity will begin.
Data Date (DD). The point in time that separates actual (historical) data from future (sched-
uled) data. Also called as-of date.
Definitive Estimate. See estimate.
Deliverable. Any measurable, tangible, verifiable outcome, result, or item that must be pro-
duced to complete a project or part of a project. Often used more narrowly in ref-
erence to an external deliverable, which is a deliverable that is subject to approval by
the project sponsor or customer.
Dependency. See logical relationship.
Dummy Activity. An activity of zero duration used to show a logical relationship in the arrow
diagramming method. Dummy activities are used when logical relationships cannot
be completely or correctly described with regular activity arrows. Dummies are
shown graphically as a dashed line headed by an arrow.
Duration (DU). The number of work periods (not including holidays or other non-working pe-
riods) required to complete an activity or other project element. Usually expressed
as workdays or workweeks. Sometimes incorrectly equated with elapsed time. See
also effort.
Duration Compression. Shortening the project schedule without reducing the project scope.
Duration compression is not always possible and often requires an increase in pro-
ject cost.
Early Finish Date (EF). In the critical path method, the earliest possible point in time on which
the uncompleted portions of an activity (or the project) can finish based on the net-
work logic and any schedule constraints. Early finish dates can change as the project
progresses and changes are made to the project plan.
Early Start Date (ES). In the critical path method, the earliest possible point in time on which
the uncompleted portions of an activity (or the project) can start, based on the net-
work logic and any schedule constraints. Early start dates can change as the project
progresses and changes are made to the project plan.