What is the main use of a sequence diagram in UML?

A sequence diagram in UML (Unified Modeling Language) is primarily used to illustrate the flow of events within a system over time. It focuses on how different objects interact with one another through messages exchanged during a specific scenario or process. The sequence diagram emphasizes the order of these interactions, which helps developers and stakeholders understand the dynamic behavior of the system.

This diagram typically displays objects as vertical lines and represents the messages exchanged between them as horizontal arrows. By visualizing the sequence of operations, it aids in capturing the details of complex interactions and clarifying how processes unfold in various scenarios, making it easier to identify requirements and design solutions effectively.

Other options, while relevant in different contexts of UML, do not accurately capture the main purpose of a sequence diagram. For instance, representing overall system architecture is more suited to component or deployment diagrams, while class structure is depicted in class diagrams, and user interactions are often illustrated using use case diagrams. Each of these serves a distinct purpose in the broader scope of UML.