Which of the following is a valid description of a create message?

Which of the following is a valid description of a create message?

• A. Dashed line with an open arrowhead indicating creation of a new instance
• B. Solid line with a filled arrowhead indicating creation of a new instance
• C. Dashed line with a closed arrowhead indicating error
• D. Solid line with an open arrowhead indicating a reply

Answer: (A)

A create message is shown with a dashed line ending in an open (hollow) arrowhead. This notation signals that a new object is being instantiated as a result of the message, and the new object's lifeline begins at that moment. The dashed style helps distinguish it from a normal operation call on an existing object, which uses a solid line with a filled arrowhead, and from a typical return, which is often dashed but serves a different purpose. The key idea is that the message creates something new rather than invoking something on an already existing instance, so the dashed line with the hollow arrowhead is the clearest indicator of that creation event.

A create message is shown with a dashed line ending in an open (hollow) arrowhead. This notation signals that a new object is being instantiated as a result of the message, and the new object's lifeline begins at that moment. The dashed style helps distinguish it from a normal operation call on an existing object, which uses a solid line with a filled arrowhead, and from a typical return, which is often dashed but serves a different purpose. The key idea is that the message creates something new rather than invoking something on an already existing instance, so the dashed line with the hollow arrowhead is the clearest indicator of that creation event.