The Extended Research Of Description Logic Under The Framework Of The Rough Set

The semantics and reasoning of rough description logic for the semantic Web, and the construction of rough description logics framework under formal concept structure on the domain of objects are studied in this thesis. The main contributions of this thesis are as follows.?1?The reasoning algorithm about conceptual satisfiability of traditional rough description logics is modified, where the sub-concepts and the rules of a concept are the only thing it ever needed to determine its satisfiability. The validity of the modified algorithm is stated, and its validity is illustrated through an example.?2?With the extensions of formal concepts are seen as the concepts of description logic, we combine Formal Concept Analysis and Rough Set Theory to establish two new RDLs. The approaches proposed by Y. Y. Yao are applied in the frameworks of the new RDLs, where the upper and lower approximations of a non-definable concept are defined by lattice-theoretical operators and set-theoretical operators, respectively, and particularly, a new form of lower approximation which is different from the previous form is defined. The notions are very different from the classical form, but it is pretty practical. Based on the novel notions of the upper and lower approximations, we add the approximation operators to the structure of Description Logic. Then two new RDLs,Fl_ALC andFs_ALC are established. The corresponding semantic and syntax are given. At last, we provide an extended tableaux algorithm, which can be used to solve some related reasoning problems.?3?A new definition about definable concept and non-definable concept is given in formal concept structure on the domain of objects, and a pair of operators are created to approximate non-definable concepts. With the whole formal concept seen as the concept of description logic, we introduce the new defined operators are introduced to the structure of Description Logic and a new RDLs,F_ALC is established. The corresponding semantic and syntax are given. The reasoning algorithm about concept satisfiability is extended to solve the reasoning problem.