A Notation for Describing Aggregate Relationships in an Object-Oriented Data Model

The emphasis in object-oriented databases (OODBs) is on the inheritance, or "is a," type of relationship; yet, many relationships within databases are of the aggregate type—e.g., "is a part of" and "is associated with." While the semantics of the inheritance relationship is directly supported by OODB systems, the semantics of aggregate relationships must often be implemented again and again by application programmers. To address this problem, this paper proposes a notation for describing the semantics of a taxonomy of aggregate relationship types. The notation can be incorporated into an Object-Relationship Diagram (ORD) and an Object-oriented Database Definition Language (ODDL) to provide enhanced conceptual models for OODB design and improved support of aggregate relationships by an extended OODB system. Such support can significantly ease database applications development and improve the integrity of database operation.