Timed out notification or subprocess activities are initially detected by the background engine. Background engines set up to handle timed out activities periodically check for activities that have time out values specified. If an activity does have a time out value, and the current date and time exceeds that time out value, the background engine marks that activity's status as 'TIMEOUT' and calls the Workflow Engine. The Workflow Engine then resumes by trying to execute the activity to which the <Timeout> transition points.
