Relationships in use-case diagrams

In UML, a relationship is a connection between model elements. A UML relationship is a type of model element that adds semantics to a model by defining the structure and behavior between the model elements.

UML relationships are grouped into the following categories:

Category	Function
Activity edges	Represent the flow between activities
Associations	Indicate that instances of one model element are connected to instances of another model element
Dependencies	Indicate that a change to one model element can affect another model element
Generalizations	Indicate that one model element is a specialization of another model element
Realizations	Indicate that one model element provides a specification that another model element implements
Transitions	Represent changes in state

You can set properties and use keywords to create variations of these relationships.

The following topics describe the relationships that you can use in use-case diagrams: