The development of information society in recent decades has enabled collecting, filtering and storing huge amounts of data. These data must be further processed to gain valuable information and knowledge. The scientific field dealing with extracting information and knowledge from data has evolved rapidly to cope with the extent and growth of information sources the number of which has geometrically increased with the appearance of the World Wide Web. All traditional approaches in information retrieval, knowledge acquisition, and data mining must be adapted for the dynamic, heterogeneous, and...