An Extended Rough Sets Approach to Analysis of CUDT
Classical Rough Sets Theory (CRST) is thought to be an effective mathematical approach to discovering rules from Decision Table (DT). Every entry in DT must be unique and certain qualitative value of attribute. However, there are always heterogeneous entries in DT from complex decision problem, that is, entries with a continuous quantitative attribute, unknown entries or multi-valued entries, and these types of entries often occur in same DT. The DT with these entries named Continuous Uncertain Decision Table (CUDT) cannot be analyzed directly by CRST. Fortunately, by modeling those three types of entries in CUDT with Fuzzy Sets theory (FST), we found that CUDT can be transformed into a special DT called Extended Decision Table (EDT) in which each entry is associated with a membership degree. An extended CRST is proposed to transform the CUDT into EDT and to calculate the lower approximations and the boundaries of decision concepts in EDT.
Key wordscontinuous uncertain decision system extended Rough Sets Approach Approximation of concepts
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