What is the notation of a synchronous message in a sequence diagram?

What is the notation of a synchronous message in a sequence diagram?

• A. Solid line with a filled-in arrowhead
• B. Solid line with an open arrowhead
• C. Dashed line with an open arrowhead
• D. Dashed line with a filled arrowhead

Answer: (A)

In sequence diagrams, the way a message is drawn communicates its timing. A synchronous call is shown as a solid line with a filled arrowhead, which tells you the sender waits for the callee to finish before moving on. This is exactly what synchronous behavior implies in practice. An open arrowhead on a solid line indicates an asynchronous message, where the sender continues without waiting. Dashed lines are used for non-primary flows like returns, often with an open arrowhead to show the reply path. So the notation described—solid line with a filled arrowhead—best represents a synchronous message.

In sequence diagrams, the way a message is drawn communicates its timing. A synchronous call is shown as a solid line with a filled arrowhead, which tells you the sender waits for the callee to finish before moving on. This is exactly what synchronous behavior implies in practice. An open arrowhead on a solid line indicates an asynchronous message, where the sender continues without waiting. Dashed lines are used for non-primary flows like returns, often with an open arrowhead to show the reply path. So the notation described—solid line with a filled arrowhead—best represents a synchronous message.