A New Approach for N-ary Relationships in Object Databases

In an object-oriented or object-relational database, an n-ary relationship among objects is normally represented in a relation that is separated from other properties of objects at the logical level. In order to use such a database, the user needs to know the structure of the database, especially what kind of relations and classes there are, how they are organized and related in order to manipulate and query object data. To make the logical level closer to the conceptual level so that the database is easier to use, we propose a novel approach that allows the user to represent n-ary relationships among objects in their class definitions so that the user can directly manipulate and query objects based on the class definitions, rather than explicitly join relations at the logical level. Based on the class definitions, the system can automatically generate the modified class/object relation definitions and the corresponding regular relation definition for the n-ary relationship at the physical level to reduce redundancy and convert data manipulation and query statements based at the logical level to ones at the physical level.