UML sequence diagram - Checking process

"A schedule or timetable is a basic time management tool consisting of a list of times at which possible tasks, events, or actions are intended to take place, or a sequence of events in the chronological order in which such things are intended to take place. The process of creating a schedule - deciding how to order these tasks and how to commit resources between the variety of possible tasks - is called scheduling, and a person responsible for making a particular schedule may be called a scheduler. Making and following schedules is a fundamental human activity, and learning to do these things effectively is one of the most basic life skills. There are a wide variety of situations in which schedules are necessary, or at least useful.
Schedules are useful for both short periods, such as a daily or weekly schedule, and for long term planning with respect to periods of several months or years. They are often made using a calendar, where the person making the schedule can note the dates and times at which various events are planned to occur. Schedules that do not set forth specific times for events to occur may instead list an expected order in which events either can or must take place." [Schedule. Wikipedia]
The UML sequence diagram example "Checking process" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the Rapid UML solution from the Software Development area of ConceptDraw Solution Park.

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.