What is a message receive occurrence?

What is a message receive occurrence?

• A. Exists on a lifeline at the point where the arrowhead end of a message meets the lifeline
• B. Exists on a lifeline at the point where the tail end of a message meets the lifeline
• C. Is only shown for asynchronous messages
• D. Occurs at the end of the lifeline

Answer: (A)

In a sequence diagram, every message is drawn as an arrow from a sender lifeline to a receiver lifeline. The message receive occurrence is the point on the receiver’s lifeline where the arrowhead meets it—the moment the receiver handles the message. This is the receiving event, not the sending one (which happens at the tail of the arrow on the sender lifeline). It applies to both synchronous and asynchronous messages, so it isn’t limited to one type. It isn’t at the end of the lifeline; it’s precisely where the arrowhead touches the receiver lifeline.

In a sequence diagram, every message is drawn as an arrow from a sender lifeline to a receiver lifeline. The message receive occurrence is the point on the receiver’s lifeline where the arrowhead meets it—the moment the receiver handles the message. This is the receiving event, not the sending one (which happens at the tail of the arrow on the sender lifeline). It applies to both synchronous and asynchronous messages, so it isn’t limited to one type. It isn’t at the end of the lifeline; it’s precisely where the arrowhead touches the receiver lifeline.