Arcs or relationships connecting nodes in the graph are displayed as lines. Arcs can be of various types, as specified in the domain model; they are distinguished with customizable colors. An arc is only drawn if both node endpoints are visible in the window.
Arcs are also directed. An arc from source node A to destination node B is represented as a line from the bottom of node A to the top of node B. Node A is called a client of node B and node B is called a supplier of node A. The arc is an outgoing arc of node A and an incoming arc of node B. A node may have an arc going to itself, for a recursive relationship. You see this as a line from the bottom of a node to its top.
When working with arcs, you need to select them before applying an operation.