ER model clustering as an aid for user communication and documentation in database design
Toby J. Teorey, Guangping Wei, Deborah L. Bolton, John A. Koenig · Communications of the ACM · 1989
Entity-relationship clustering promotes the simplicity that is vital for fast end-user comprehension, as well as the complexity at a more detailed level to satisfy the database designer's need for extended semantic expression in the conceptual model.