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 is a topological space generated by a partition, called a clopen space. For LNS,it is a generalized/pretopological space which is more general than topological space. For GrCC,there are two possibilities. One is a special case of LNS,which is the topological space generated by the covering. There is another topological space, the topology generated by the finite intersections of the members of a covering. The first one treats covering as a base, the second one as a subbase.(4)Knowledge representations in RST are symbol-valued systems. In GrCC, they are expression-valued systems. In LNS, they are multivalued system; reported in 1998.(5)RST and GRCC representation theories are complete in the sense that granular models can be recaptured fully from the knowledge representations.