Class method interactions

Certain classes define one or more methods. If so, you will see them on the relevant class diagram underneath the attribute compartment. When a method is called, it is invoked on a specific instance of its class. Unlike an event which is dispatched and serviced asynchronously, a method is called directly from the action language within some activity of a state or by a domain or external entity operation. The method executes within the activity's context immediately returning any values that may be defined, much like calling a function or method in a programming language.

This sort of interaction can be represented on the collaboration diagram. It will be associated with an arrow with a solid arrow head to denote that it is a synchronous interaction, as opposed to a singal/event type of interaction.

To keep a collaboration diagram from being too cluttered, interaction parameters are often omitted. In the example above, the method call parameters that you see on the class diagram do not appear.