Study Of Attributes Reduction In Rough Sets Theory

People can obtain, store and deal with a great deal of data more easily in the information times, and the data increase every day. But does it mean that we have had enough knowledge? It doesn't. Although we have enough data, we have little knowledge from these data. We have to need a tool or method which can be used to distill knowledge from these increasing and unorderly data. The distilled knowledge. should be useful and interesting that can be used for making decisions in production and life.After 50 in the last century, people tried to use many methods such as neural network, statistics study, and support vector machine and so on to discover knowledge. But the obtained knowledge is latent and can not be understood well by people.Rough sets theory is a mathematic tool which is proposed in 1982 by Z. Pawlak who is a mathematician in Poland, and this tool is used to process half-baked and imprecise data. It needn't experts' knowledge and reasons from special organs; it can be used to obtain a new information system which equals to the original information system in expression something. And more, using it, we can obtain knowledge that is understood rules, and these rules accord with people's experiences and more fitful in decision making.Although rough sets theory has been used in many commercial fields and it can be used to process imprecise and imperfection data, there are still some aspects that can be studied in rough sets theory. Such as improving the attributes reduction methods in general information systems, so as to these methods can be used in decision information systems and so on. This paper proposes a new method about attributes reduction which can be used in a general information system or a consistent decision information system, and a new method about how to obtain binary discernibility matrix in inconsistent decision information systems.Also in 1982, concept lattices theory is proposed to obtain some rules from data. And these rules are also understood, so rough sets theory and concept lattices theory develop rapidly these 20 years.For a formal context, its concepts are stated. But if we delete some attributes or objects, its concepts are changed. This paper analyses the concepts changing cases when we delete some attributes or objects from a formal context.