[ fromfile: introuml.xml id: umlrelationships ]

UML is especially good at describing relationships between classes. Jumping ahead a bit to Example 2.21, we will describe the subobject relationship in UML. Because the subobjects are strictly part of the parent object, and cannot possibly exist as standalone objects, we can use the composition relationship. In Figure 2.2, the filled-in diamond indicates that the instances of that class are composed (partially) of instance(s) of the class on the other end of the relationship.

Figure 2.2.  Composition