Institute of Information Science, Academia Sinica, Taipei 115, Taiwan, Republic of China. clarkkuo@iis.sinica.edu.tw|Institute of Information Science, Academia Sinica, Taipei 115, Taiwan, Republic of China. clarkkuo@iis.sinica.edu.tw|Institute of Information Science, Academia Sinica, Taipei 115, Taiwan, Republic of China. clarkkuo@iis.sinica.edu.tw|Institute of Information Science, Academia Sinica, Taipei 115, Taiwan, Republic of China. clarkkuo@iis.sinica.edu.tw