What in a lifeline?

What in a lifeline?

• A. Represents a single instance that participates in an interaction by exchanging messages with other lifelines
• B. Depicts a data store in the activity diagram
• C. Indicates a control node
• D. Denotes a constraint

Answer: (A)

In a UML interaction diagram, a lifeline represents a single instance that participates in the interaction by exchanging messages with other lifelines. It’s shown as a vertical dashed line for the duration of the interaction, often with an activation bar to indicate when that instance is performing work. This is what distinguishes a lifeline from other diagram elements: data stores belong to activity diagrams and show where data is kept, control nodes indicate control flow like decisions or forks in an activity, and constraints express conditions or rules on the model. So the lifeline is all about the participation of one specific object or instance in the message exchanges.

In a UML interaction diagram, a lifeline represents a single instance that participates in the interaction by exchanging messages with other lifelines. It’s shown as a vertical dashed line for the duration of the interaction, often with an activation bar to indicate when that instance is performing work. This is what distinguishes a lifeline from other diagram elements: data stores belong to activity diagrams and show where data is kept, control nodes indicate control flow like decisions or forks in an activity, and constraints express conditions or rules on the model. So the lifeline is all about the participation of one specific object or instance in the message exchanges.