I have the same need. For example, can I have version 1.0 with Category A and B; then create version 1.1 and add Category C (so now I have A, B and C). Then create version 1.2 and remove Category B, leaving only A and C. So someone can search on Category A and get all three versions; search on Category B and get only version 1.0 and 1.1; search on Category C and get only version 1.2. In other words, can each version "remember" the categories assigned at the time it was created?