Research On The Extension Of Several Rough Set Models

Rough set theory is an important theoretical knowledge to solve incomplete information,the generalization degree of rough set model plays an important role in dealing with uncertain information problem.Therefore,this thesis studies the model from the following three perspectives:1.The research on covering rough sets model has gained abundant achievements,this article is based on covering rough fuzzy set model,extending from a single domain to two domains,and the operator properties of the new model are also discussed,thus,generalizing and enriching the model system of covering rough sets.2.A model based on the combination of rough sets and fuzzy sets,and put forward a new model in the case that both the knowledge set and the approximation set are also fuzzy.Specifically,we first divide the domain into fuzzy sets and get the correspon ding fuzzy knowledge sets,then,a new rough set model is proposed based on the concept of fuzzy nearness and the properties of the related operators of the model are also studied,finally,an example is given to illustrate the application of the new model in real life3.Dealing with incomplete information systems is one of the main applications of rough sets,the rough set model is extended,which plays a key role in solving the problem in different relations.In this thesis,a new multi granularity rough set model is established based on an improved restricted tolerance relation and the properties of the model operator are also discussed,moreover,we study the intrinsic relationship between the new model and the three relational models,finally,the advantages of the new model are illustrated by dealing with incomplete information tables.