=+S. Start the journey and keep an eye on progress. According to the journey plan derived from the completion of the previous steps, we can now begin the journey. However, in order successfully to reach B, we have to monitor continuously the progress of the journey. On our way we may have to alter the original journey plan taking into account any change of circumstances, such as delays or cancellations. We may even have to change the location of the destination altogether because of some unforeseen problem.