Validity of Activity Diagram with "Accept Event" and "Send Signal" actions

Question

I'm describing the "Performing check-in" use case of a Boarding System. This is what I've done:

Basically a Passenger puts the ticket code into a Kiosk that interacts with the Boarding System (software). The Kiosk has a printer and a display.

Is this diagram correct? Specifically, are the connections between the "Accept Event" and "Send Signal" correct? Are the ending nodes correct?

I've also developed two alternatives:

Which diagram is the best descriptor of the above use case? I'd say the second one because the two "Send Signal" actions ("Issue" and "Error") of the Boarding System are asynchronous with the Kiosk.

Answer 1

If you show messages as links, you needn't show them simultaneously as blocks with extra angles(in or out). Look here

Your ending nodes are OK.