I am trying to model a call where a synchronous call is made to a server which is handled in a single thread with a mailbox. It fires an asynchronous call off, and eventually receives another asynchronous message with the response, then the synchronous call returns. I'm not sure if this is possible to model directly, an asynchronous message to an existing life line. Showing the mail box as a discrete actor is not an appropriate detail.
Product: Astah Professional