Implementation of object-oriented association relationships in relational databases

With the increasing popularity of object-relational technology, it is becoming important to have a methodology which allows designers to exploit the great modelling power of object-oriented conceptual models (OOCMs) and yet which still facilitates implementation on relational database systems. This paper presents a practical solution for the implementation of different types of object-oriented association relationships, which include a wide range of collection types (i.e. sets, lists, arrays and bags), into relational database tables. The implementation strategies raise a number of constraints relating to data integrity in the database system. These constraints are associated with (i) normalisation of the resulting relational tables, and (ii) data integrity after insertion/deletion. In order to ensure completeness of the strategies, some techniques for the implementation of inverse traversal in association relationships are also provided. An example is used throughout this paper to demonstrate and evaluate the proposed method