An implementation of the entity-relationship model in type theory

The entity-relationship (ER) model has evolved from a database design tool to full-fledged database model. Existing prototypes of ER-based database systems use either relations or other record structures in the internal schema. Purely record based mappings are not adequate for supporting the rich semantics of the ER model in a natural way. The use of a rich and extensible type of system for the internal level representation of an ER database system is described. It is shown that the constructs of the ER model can be directly mapped to the internal level without loss of semantics. An algebra for data manipulation that has been implemented in a prototype of the ER database system based on a formal theory of types is discussed