After some initialization, a long running business process needs further input from the client. The process should only wait for a certain period of time. If that time has passed without further user input, default processing should start. Which BPEL construct can most effectively handle this situation?

In BPEL, a 'pick' activity (often called 'receive choice') with an 'onAlarm' event handler (timeout element) is the standard construct for waiting for multiple possible events with a time limit. If the timeout expires before the message arrives, the onAlarm branch executes, enabling default processing. Parallel wait or subsequent wait activities don't provide the same event-driven timeout behavior.