Connecting lines between entities indicates a relationship exists between the entities. The degrees of relationship (cardinality) are displayed by the symbols next to the entities on the connecting relationship line.
Indicates: one or zero. |
|
Indicates: zero or many. |
|
Indicates: one and only one. |
|
Indicates: one or many. |
A closed arrow next to an entity indicates an inheritance relationship. In the example below, the closed arrow indicates that the Analyzer, Relief_Valve, Pressure, and so forth, inherits structure and behavior from the Process Data General entity.