Arrow Diagramming Method (ADM): A network diagramming technique in which activities are represented by arrows.
It is used for scheduling activities in a project plan.
The precedence relation between activities is represented by circles connecting to one or more arrows.
sometimes a "dummy task" is added, to represent a dependency between tasks, which does not represent any activity.
Figure 1: ADM example
see also: Precedence_Diagram_Method for similar concept.