Composition

The Composition relationship is used to model the concept that “X is composed of Y”. For example, a Car is made up of a number of Widgets.

This can be drawn in either of the following ways in the Business Object Modeler:

  • In the first example, there is a line drawn between the Car and Widgets, which is labeled "parts".
  • In the second example, there is a "parts" attribute in the Car class.
    Note: At runtime, these two approaches are treated identically. It does not matter which is used.

The Composition relationship is also known as the Containment relationship.