Granular Computing on partitions (RST), coverings (GrCC) and neighborhood systems (LNS) are examined: 1. The order of generality is RST, GrCC, and then LNS 2. The quotient structure: In RST, it is called quotient set. In GrCC, it is a simplical complex, called the nerve of the covering in combinatorial topology. For LNS, the structure has no known description. 3. The approximation space of RST ...