This Interaction Overview Model provides an overview of the control flow, with nodes representing interactions or interaction uses. [UML 2.4.1 Specification] refers to these diagrams as interaction diagrams in some places, while interaction overview diagrams are known as specialization of activity diagrams in others. Interaction overview diagrams resemble activity diagrams in that they can only contain inline interactions or interaction uses rather than invocation actions. Inline interactions and interaction uses are distinct call behavior action types. For interaction overview diagrams to be properly nested, UML 2.4 requires branching and joining of branches. This is more restrictive than activity diagrams and may be difficult to follow.