Interaction Overview Diagrams
Interaction overview diagrams provide overview of the flow of control where nodes of the flow are interactions or interaction uses. [UML 2.4.1 Specification] in some places relegates these diagrams as interaction diagrams while in other places interaction overview diagrams are referred to as specialization of activity diagrams.
Interaction overview diagrams do look like activity diagrams that can only have inline interactions or interaction uses instead of invocation actions. The inline interactions and interaction uses are considered as special forms of call behavior action. (It seems that UML 2.4 specification mistakenly refers to those as either object nodes - which sounds weird - or ActivityInvocations - which are simply absent in UML 2.4.)
UML 2.4 requires branching and joining of branches in interaction overview diagrams to be properly nested. This is more restrictive than in activity diagrams and could be quite difficult to obey.
You can find some examples of interaction overview diagrams here:
Interaction overview diagrams are framed by the same kind of frame that encloses other forms of interaction diagrams - a rectangular frame around the diagram with a name in a compartment in the upper left corner. Interaction kind is interaction or sd (abbreviated form). Note, that UML has no io or iod abbreviation as some would expect.
Interaction overview diagram Online Shopping
The heading text may also include a list of the contained lifelines (that do not appear graphically).
Elements of Activity Diagram
Interaction overview diagrams are defined as specialization of activity diagrams and as such they inherit number of graphical elements.
Interaction overview diagrams can only have inline interactions or interaction uses instead of actions, and activity diagram actions could not be used.
The following elements of the activity diagrams could be used on interaction overview diagrams:
Elements of Interaction Diagram
The following elements of the interaction diagrams could be used on interaction overview diagrams:
An interaction diagram of any kind may appear inline as an invocation action. The inline interaction diagrams may be either anonymous or named.
Interaction Add Item to Shopping Cart may appear inline on some interaction overview diagram
An interaction use may appear as an invocation action.
Interaction use Add Item to Shopping Cart may appear on some interaction overview diagram
Some UML tools may choose to "explode" the interaction use into an inline interaction with the name of the interaction referred by the use. The inline interaction will have arguments (if any) of the reference replaced with parameters.