Institute of Systems Science, National University of Singapore, 25 Heng Mui Keng Terrace, Singapore. olivo@nus.edu.sg|Institute of Systems Science, National University of Singapore, 25 Heng Mui Keng Terrace, Singapore. olivo@nus.edu.sg|Institute of Systems Science, National University of Singapore, 25 Heng Mui Keng Terrace, Singapore. olivo@nus.edu.sg