Sequence diagrams are used to illustrate the dynamic behavior of the system, showing how objects interact with each other in a specific sequence of events. Here are the main components:
Objects: They are represented as rectangles at the top of the diagram.
Lifelines: Vertical dashed lines represent the life of an object during the interaction.
Activation bars: Thin rectangles on a lifeline represent the period during which an element is performing an operation.
Messages: Horizontal arrows between lifelines represent communication between objects. The arrow direction shows the message direction, and the label indicates the operation or event.
Return messages: Dashed horizontal lines with arrowheads represent return messages.