Interaction overview diagram

Interaction Overview Diagram in the Unified Modeling Language (UML) is a type of activity diagram in which the nodes represent interaction diagrams. They are a high level structuring mechanism for sequence diagrams. Interaction overview diagrams illustrate an overview of a flow of control in which each node can be an interaction diagram.^[1]

Interaction Overview Diagrams combine activity diagram and in-line sequence diagrams. These interaction diagrams can include sequence, communication, interaction overview and timing diagrams. In the diagram nodes are interactions of sequence diagrams, and the edges show the order in which these interactions occur. You can also use an interaction overview diagram to deconstruct a complex scenario that would otherwise require multiple if-then-else paths to be illustrated as a single sequence diagram.^[2]

Most of the notation for interaction overview diagrams is the same for activity diagrams. For example, initial, final, decision, merge, fork and join nodes are all the same. However, interaction overview diagrams introduce two new elements: interaction occurrences and interaction elements.^[3]