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Object Containment

  1. Objects that contain other objects are called complex or composite objects. There can be multiple levels of containment, forming a containment hierarchy among objects.
  2. Example: A bicycle design database:

    Figure 8.6:  Containment hierarchy for bicycle-design database.

    Fig. 8.6 shows the containment relationship in a schematic way by listing class names. Thus the links between classes must be interpreted as is-part-of, rather than the is-a interpretation of links in an inheritance hierarchy.

  3. 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.

  4. 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.

Osmar Zaiane
Mon Jun 29 17:30:13 PDT 1998