Gantt charts for planning and scheduling

This section describes the use of Gantt charts for planning and scheduling.

A Gantt chart is a time and activity bar chart that is used for planning, and controlling projects or programs that have a distinct beginning or end. In a Gantt chart, each main activity that is involved in the completion of the overall project or program is represented by a horizontal bar. The ends of the bar represent the start and end of the activity.

Gantt chart views in Decision Optimization Center, are either Resource-oriented or Activity-oriented. In a resource-oriented Gantt chart view, resources are listed along the vertical axis with time or activities listed along the horizontal axis. In an activity-oriented Gantt chart view, activities are listed along the vertical axis with time or resources listed along the horizontal axis.


An activity 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 sub-activities. A subactivity, or child activity, can in turn be a parent activity of other sub-activities 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 0. A zero-duration activity is commonly called a milestone. Typically, milestones are not rendered by the same renderer as activities with a nonzero duration.


A resource 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 can group resources by physical location or by type of machinery.


A constraint is a type of condition set between two activities. Constraints are often 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. A reservation represents the assignment of one resource to one activity.

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.