Defines activities in the data model.
is a task to be completed. Activities are
hierarchical in nature. This means that a main activity, called parent activity
, can be broken down into subactivities. A
subactivity, or child activity
, can in turn be a parent activity of other
subactivities or, if it is at the very end of a branch of the hierarchy,
it is a leaf activity. A leaf activity
is an activity that has no child activity
In addition to its name and identifier, an activity is
defined by its start time
and end time
, which determine an interval called the duration
of the activity. If the start and end times
are identical, the duration is equal to
. A zero-duration activity
is commonly called a milestone
. Typically, milestones are not rendered by
the same renderer as activities with a non-zero duration.
is a means by which an activity can be completed.
Resources can be persons, premises, equipment, and so forth. Like
activities, resources are also hierarchical in nature.
If resources are people, the parent resource
is a department while the child resources
are the individual employees. Likewise, you may want to group resources
by physical location or by type of machinery.
is a type of condition set between two activities.
Constraints are represented by arrowed polyline links.
Constraints can have one of the following types:
start to start
start to end
end to start
end to end
The source activity—that is, the activity whose
start or end controls the start or end of another activity—is
called the From activity
. Conversely, the target activity—that
is, the activity whose start or end depends on the start or end of
another activity—is called the To activity
When a resource is assigned to an activity, this assignment
is called a reservation
. In the terminology of JViews Gantt
, a reservation represents the assignment
An activity can have multiple resources reserved and
similarly, a resource can be reserved for more than one activity.
The activity that reserves the resource cannot be changed after the
reservation is created.