At what point can a destruction occurrence appear in a lifeline?

A destruction occurrence signifies the end of an object's life in a sequence diagram and can only appear as the last event on a lifeline. This is because a lifeline represents a particular instance of a classifier, and its destruction indicates that the instance will no longer be available to participate in subsequent interactions or message exchanges.

By placing the destruction occurrence at the end of the lifeline, the model clearly communicates that all interactions associated with that instance have concluded. Any events or messages that are to follow must be associated with a different lifeline or instance, as the original instance is no longer in existence after its destruction.

In contrast, the nature of lifelines prevents destruction occurrences from appearing at the start or in the middle of message exchanges, as these points imply that the instance is still active and able to interact with others. Thus, the correct understanding of the placement of destruction occurrences in sequence diagrams emphasizes that they can only occur after all relevant events have taken place, making them the terminal point of the lifeline.