∗-reductions in a knowledge base

One of the advantages of rough set theory is the fact that an unknown target concept can be approximately characterized based on existing knowledge structures in a knowledge base. Knowledge reductions are one of the key problems in the study of rough set theory. In this paper, ∗-reductions and their features in a knowledge base are explored. Moreover, communication between knowledge bases is proposed based on the use of homomorphisms between relation information systems, and several invariant characterizations under homomorphisms are obtained. These results will be significant for establishing a framework for granular computing in knowledge bases.