sets i / 1 * 2 / j / j1 * j5 / ij(i,j) 'effectively defines a subset of j for each i' / 1.(j1,j2,j3) 2.(j1,j4,j5) / ; parameter c(j) b(i) ; c(j) = ord(j); b(i) = sum{ij(i,j), c(j)};