“…Just as a big umbrella it covers all the research on the theories, methodologies, technologies, and tools about granules, especially, under the concept of GrC, L. Zhang and B. Zhang [18][19][20][21][22][23][24] focus on the equivalence relationship among different grain-size worlds and on the problem that is mainly based on fuzzy sets, i.e., quotient space theory, fuzzy quotient space. In quotient space theory, hierarchical structures are expressed by the relationship on crisp sets in [20,24], and it is a core concept. The matrix is objective, operative, and can describe binary relations on crisp sets.…”