Relationship among entities : A relationship is any association, linkage, or connection between the entities of interest to the business; it is a two- directional, significant association between two entities, or between an entity and itself. Each relationship has a name, an optionality (optional or mandatory), and a degree (how many).A relationship is described in real terms.
Assigning a name, optionality, and a degree to a relationship helps confirm the validity of that relationship. If you cannot give a relationship all these things, then perhaps there really is no relationship at all.
Relationship represents an association between two or more entities. An example of a relationship would be:
- Employees are assigned to projects
- Projects have subtasks
- Departments manage one or more projects