Name 

Description 

Deferred Event (UML 1.5 Activity Diagram) 

A deferred event is like an internal transition that handles the event and places it in an internal queue until it is used or discarded.
A deferred event may be thought of as an internal transition that handles the event and places it in an internal queue until it is used or discarded. You can add a deferred event to a state or activity element. 

State (UML 1.5 Activity Diagrams) 

A state models a situation during which some (usually implicit) invariant condition holds. The invariant may represent a static situation such as an object waiting for some external event to occur. However, it can also model dynamic conditions such as the process of performing some activity (for example, the model element under consideration enters the state when the activity commences and leaves it as soon as the activity is completed). 

Transition (UML 1.5 Activity Diagrams) 

A single transition comes out of each state or activity, connecting it to the next state or activity.
A transition takes operation from one state to another and represents the response to a particular event. You can connect states with transitions and create internal transitions within states. 

UML 1.5 Activity Diagram Definition 

This topic describes the UML 1.5 Activity Diagram. 

UML 1.5 Activity Diagram Elements 

The table below lists the elements of UML 1.5 Activity diagrams that are available using the Tool Palette.
UML 1.5 activity diagram elements