#ERD
#ERD #ERDiagram #Roles #DBMS Roles in ER Diagram
The function that an entity plays in a relationship is called its role. Roles are normally explicit and not specified.
They are useful when the meaning of a relationship set needs clarification.
For example, the entity sets of a relationship may not be distinct. The relationship works-for might be ordered pairs of employees (first is manager, second is worker).
In the E-R diagram, this can be shown by labelling the lines connecting entities (rectangles) to relationships (diamonds).
Source: Database System Concepts | 6th Edition Book by Henry F Korth