IDEF1X is based on the relational data model designed by E. F. Codd and on the entity-relationship model designed by Peter Chen, but IDEF1X models differ from the models on which IDEF1X is based. A model created using Peter Chen’s or E.F.Codd’s designs will appear different compared to a model created using ER/Studio DA and the IDEF1X notation, and vice versa.
IDEF1X makes it easier to visualize primary and foreign keys. IDEF1X also offers the power (and danger) of using identifying relationships to cascade primary keys through a chain of entities.