Chapter 10. Interaction Diagrams

A fundamental goal of UML 2.0 is to allow users to capture more than just structural relationships. UML 2.0 is intended to capture processes and flows of events. Interaction diagrams draw from nearly every other facet of the language to put together a set of diagrams that capture communications between objects. UML 2.0 has greatly expanded UML 1.x’s ability to describe complex flow of control; one of the largest sections of the UML 2.0 specification is the interaction diagrams section. Because of the expanded functionality, quite a bit of new terminology has been introduced. We’ll cover all the terms in this chapter and try to give you a feel for what terms are really critical and which are there to formalize the specification.

What Are Interactions?

Interaction diagrams are defined by UML to emphasize the communication between objects, not the data manipulation associated with that communication. Interaction diagrams focus on specific messages between objects and how these messages come together to realize functionality. While composite structures show what objects fit together to fulfill a particular requirement, interaction diagrams show exactly how those objects will realize it.

Interaction diagrams are typically owned by elements in the system. For example, you may have an interaction diagram associated with a subsystem that shows how the subsystem realizes a service it offers on its public interface. The most common way of associating ...

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