Pyramid Diagrams

The vector stencils library "UML interaction overview diagrams" contains 13 symbols for the ConceptDraw PRO diagramming and vector drawing software.
"Interaction Overview Diagram is one of the fourteen types of diagrams of the Unified Modeling Language (UML), which can picture a control flow with nodes that can contain interaction diagrams.
The interaction overview diagram is similar to the activity diagram, in that both visualize a sequence of activities. The difference is that, for an interaction overview, each individual activity is pictured as a frame which can contain a nested interaction diagrams." [Interaction overview diagram. Wikipedia]
"Interaction diagrams.
Interaction diagrams, a subset of behavior diagrams, emphasize the flow of control and data among the things in the system being modeled:
(1) Communication diagram: shows the interactions between objects or parts in terms of sequenced messages. They represent a combination of information taken from Class, Sequence, and Use Case Diagrams describing both the static structure and dynamic behavior of a system.
(2) Interaction overview diagram: provides an overview in which the nodes represent interaction diagrams.
(3) Sequence diagram: shows how objects communicate with each other in terms of a sequence of messages. Also indicates the lifespans of objects relative to those messages.
(4) Timing diagrams: a specific type of interaction diagram where the focus is on timing constraints." [Unified Modeling Language. Wikipedia]
The example "Design elements - UML interaction overview diagrams" is included in the Rapid UML solution from the Software Development area of ConceptDraw Solution Park.