Enhancing the ER Model with Integrity Methods

Abstract

Entity Relationship (ER) schemas include cardinality constraints, that restrict the dependencies among entities within a relationship type. The cardinality constraints have direct impact on application transactions, since insertions or deletions of entities or relationships might affect related entities. Application transactions can be strengthened to preserve the consistency of a database with respect to the cardinality constraints in a schema. Yet, once an ER schema is translated into a logical database schema, the direct correlation between the cardinality constraints and application transaction is lost, since the components of the ER schema might be decomposed among those of the logical database schema. We suggest to extend the Enhanced ER (EER) data model with integrity methods that take the cardinality constraints into account. The integrity methods can be fully defined by the cardinality constraints, using a small number of primitive update methods, and are automatically created for a given EER diagram. A translation of an EER schema into a logical database schema can create integrity routines by translating the primitive update methods alone. These integrity routines may be implemented as database procedures, if a relational DBMS is utilized, or as class methods, if an objectoriented DBMS is utilized.