12. The invention defined in claim 11 wherein said assigning means is arranged to generate a sequence of pseudo-random numbers for each of said attribute values, and wherein said individual b bit binary code words include (b - K) ZEROES and K ONES, said ONES being in locations determined by the first K different numbers in said sequence.
13. The invention defined in claim 12 wherein said assigning means is arranged to combine said individual codes by locating a ONE in any location in which said individual codes have a ONE.