Entity-relationship logical design of database systems: relational normal forms and extended regular ERDs

The design of the logical structure of databases using the entity-relationship (E-R) model is considered. The goal is to focus on E-R conditions for desirable logical design, using an extended translation of the full E-R model into the more easily implementable relational database model; all entity sets in a regular E-R diagram will map to relation schemes that are in the very desirable Boyce-Codd normal form (BCNF). Conditions under which extended E-R relationship sets translate to BCNF schemes are found. These results extend to both types of weak entity sets, subset and dependent entity sets, and contribute to the logical design of robust database systems. An E-R-diagram-based design system currently under development enforces the conditions that ensure BCNF by ensuring extended regularity and other measures of well-behaved E-R models.<>