A Relationship Mechanism for a Strongly Typed Object-Oriented Database Programming Language

Object-oriented data models are receiving wide attention since they provide expressive abstraction mechanisms to model naturally and directly both structural and behavioral aspects of complex databases applications. In an objectoriented data model, a database is modeled in terms of objects grouped in classes, organized into subclasses hierarchies. Moreover, associations between entities are modeled by defining properties of objects whose value is the related object. However this way of modeling associations has several limitations which make the description of some aspects of associations unnatural. To overcome these limitations an object-relationship data model is proposed which supports both the mechanisms of an objectoriented data model and a separate mechanism to model explicitly associations and to express declaratively common constraints on them. Constructs to support this model for a statically and strongly typed object-oriented database programming language are defined.