Object Identity Object Containment Objects that contain other objects are called complex or composite objects. There can be multiple levels of containment, forming a containment hierarchy among objects. Containment hierarchy for bicycle-design database. 8.6 shows the containment relationship in a schematic way by listing class names.
Containment allows data to be viewed at different granularities by different users.
E.g., wheel by wheel designer but bicycle by a sales-person. The containment hierarchy is used to find all objects contained in a bicycle object. In certain applications, an object may be contained in several objects. In such cases, the containment relationship is represented by a DAG rather than by a hierarchy.