A precedence diagram is created using methods from graph theory, like nodes (generally represented by rectangles) and arrows. A node consists of a presentation element describing a connection point and an arrow of a presentation element to describe the relationship between two nodes. One way is a sequence of arrows (also called edges).
As a connection point or a fact, precedence diagrams recognize processes, events and arrangement relationships:
Process: Activity with determined earliest and latest start and end points.
Event: Defined and recorded state in project schedule.
Relationships: Professional, personal and technical dependencies between individual processes; always consist of exactly two nodes.
This means: nodes can be represented as either processes or events. Arrows are processes or relationships. Exactly what they are depends on the selected precedence diagram method. The process node precedence diagram has been proven in practice and distributed in project management. This precedence diagram presents processes, that means a project’s activities, through nodes, and connects them with arrows as an arrangement relationship.
Each precedence diagram always needs a start node – like the project start – an end node – its end. Then you can define, describe and place all further processes in a relationship. Only then does the actual “work” with the precedence diagram begin: the time calculations for each process node.