The Rough Sets and Knowledge Technology (RSKT) conferences serve as a - jor forum that brings researchers and industry practitioners together to discuss and deliberate on fundamental issues of knowledge processing and management and knowledge-intensive practical solutions in the current knowledge age. - perts from around the world meet annually to present state-of-the-art sci- ti c results, to nurture academic and industrial interaction, and to promote collaborative research in rough sets and knowledge technology. The main theme of the RSKT conference is to explore the synergy between rough sets and - vanced knowledge technology and applications, including knowledge discovery, datamining,knowledgeprocessingandmanagement,granularcomputing,evo- tionary computing, biocomputing and bioinformatics, cognitive computing and cognitive informatics, natural and arti cial intelligence, Web intelligence, c- plex systems, and many others. The ?rst RSKT conference was held in 2006 in Chongqing, P.R. China, f- lowed by RSKT 2007 in Toronto, Canada and RSKT 2008 in Chengdu, P.R. China. This volume contains the papers selected for presentation at the 4th - ternationalConferenceonRoughSetsandKnowledgeTechnology(RSKT2009), which was held during July 14-16 on the Gold Coast, Australia.
