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Superimposed Codewords (SIMC)

In a superimposed codewords (simc) indexing scheme
  • a tuple descriptor is formed by overlaying attribute codewords
A tuple descriptor desc(r) is
  • a bit-string, m bits long, where j ≤ nk bits are set to 1
  • desc(r) = cw(A1) OR cw(A2) OR ... OR cw(An)
Method (assuming all n attributes are used in descriptor): 

bits desc = 0 
for (i = 1; i <= n; i++) {
   bits cw = codeword(A[i])
   desc = desc | cw
}