For example, you can use a sequence diagram to create your own context to understand existing behaviors and interactions in an application, and to develop and generate new ones. You can use a sequence diagram to create a graphical representation of the behaviors and interactions between classes or interfaces in an application and to understand how the system works to accomplish the interactions.
In the interaction frame, you position instances in the interaction in any order from left to right, and then you position the messages between the instances in sequential order from top to bottom. Execution specifications appear on the lifelines and show the start and finish of the flow of control.