Study On Rough Set Theory And Its Application In Information Table Processing

Rough Set Theory, proposed by Z. Pawlak in 1982, has become a recognized and widely studied method with many publications in various fields to date. Rough set theory is a new mathematical tool to deal with the vagueness and uncertainty, it is based on the indiscernibility relation that describes indistinguishable objects, and concepts are represented by lower and upper approximations. Preliminary information about the data is not needed in rough set data analysis. The primary contributions of this thesis include:Reduction of knowledge is one of the most important topics in the research on rough set theory. An important characteristic of reduction regarding the number is demonstrated, followed by another definition of attributes significance and according heuristic algorithm. The algorithm is thoroughly analyzed. The relative reduct is discussed in a similar fashion.The classical rough set theory developed by Pawlak is based on complete information systems. In this thesis a method for incomplete information systems is proposed.The relationship of reduct and relative reduct and the upper approximation and lower approximation is discussed in the thesis, based on which a novel relative reduct-holding approximation reduct is proposed. The benefits of holding approximation reduct are explained through an example.At last the. rough sets model based on order relations is proposed normatively and discussed thoroughly with an example.