Ace the CBAP Exam 2025 – Unleash Your Business Analysis Superpowers!

In a sequence diagram, a lifeline specifically represents the existence of an object during the interactions that occur over time. It indicates the period from when the object is created until it is destroyed. This visual element is essential for understanding the duration of an object's involvement in a particular sequence of events within the system being modeled.

The lifeline is depicted as a vertical dashed line that extends downward from the object's rectangle (which indicates the class or instance). This serves as a timeline for the object, allowing analysts to visually track when messages are sent or received relative to the object's lifecycle.

While the other options touch on aspects of sequence diagrams—such as messaging and object labeling—they do not specifically describe the role of the lifeline. Instead, they pertain to different functionalities or elements within the diagram, illustrating how interactions and messages occur without addressing the concept of an object's lifecycle marked explicitly by the lifeline.