Learning UML 2.0

Chapter 11. Modeling a Class’s Internal Structure: Composite Structures

Sometimes the primary UML diagrams, such as class and sequence diagrams, aren’t a perfect match for capturing certain details about your system. Composite structures help fill some of those gaps. Composite structures show how objects create a big picture. They model how objects work together inside a class, or how objects achieve a goal. Composite structures are fairly advanced, but they’re good to have in your bag of tricks because they are perfectly suited for specific modeling situations, such as showing:

Internal structures

Show the parts contained by a class and the relationships between the parts; this allows you to show context-sensitive relationships, or relationships that hold in the context of a containing class

Ports

Show how a class is used on your system with ports

Collaborations

Show design patterns in your software and, more generally, objects cooperating to achieve a goal

Composite structures provide a view of your system’s parts and form part of the logical view of your system’s model, as shown in Figure 11-1.

Internal Structure

Chapter 5 introduced possession-related relationships between classes, including association (“has a”) and composition (“contains a”). Composite structures offer an alternate way of showing these relationships; when you show the internal structure of a class, you draw the items it possesses directly inside the class. Relationships between items in a class’s internal structure ...