Rough Sets and Knowledge Technology 4th International Conference, RSKT 2009, Gold Coast, Australia, July 14-16, 2009. Proceedings - Wen, Peng; Li, Yuefeng; Polkowski, Lech; Yao, Yiyu; Tsumoto, Shusaku; Wang, Guoyin (Springer Berlin Heidelberg : Imprint: Springer, 2009)