Developing an ER diagram involves the discovery of probably hundreds of entity types and their respective relationships. As a design nears completion, the ERD will contain hundreds of entities and relationships that crowd the diagram to the point of making it unreadable and inefficient as a communication tool. In such cas

Developing an ER diagram involves the discovery of probably hundreds of entity types and their respective relationships. As a design nears completion, the ERD will contain hundreds of entities and relationships that crowd the diagram to the point of making it unreadable and inefficient as a communication tool. In such cases, entity clusters are used to minimize the number of entities shown in the ERD. An entity cluster is formed by consolidating multiple interrelated entities into a single abstract entity object. An entity cluster is considered “virtual” or “abstract” in the sense that it is not actually an entity in the final ERD. It is a temporary entity used to depict multiple entities and relationships, with the purpose of simplifying the ERD and thus improving its readability.