Relationships, Relationship Sets and Relationship Types

Relationships, relationship sets and relationship types

A relationship is an association between two entities, for example, an entity EMPLOYEE WORKS_ON PROJECT, which is another entity. However, note that different instances of employees will be working on different projects. So an employee, John WORKS_ON Project Netlife and maybe some other employee Sara (who is also an instance of an employee) WORKS_ON Project mForm.

So we can say that relationship type is simply the relationship that exists between two entities like WORKS_ON. While the set of similar associations at a point of time is called the Relationship Set.

The illustration below will help clear up the confusion: