Abstract :
The problem of imperfect knowledge has been tackled for a long time by philosophers, logicians and mathematicians. Recently it became also a crucial issue for computer scientists, particularly in the area of artificial intelligence. There are many approaches to the problem of how to understand and manipulate the imperfect knowledge. The most successful one is, no doubt, fuzzy set theory proposed by Zadeh. Rough set theory is another attempt to this problem. The theory has attracted attention of many researchers and practitioners all over the world, who contributed essentially to its development and applications. Rough set theory overlaps with many other theories, especially with fuzzy set theory, evidence theory and Boolean reasoning methods-nevertheless it can be viewed in its own rights, as an independent, complementary, and not competing discipline
