balls.mws The four basic models Distinguishable balls (labelled structures) Distinguishable urns Indistinguishable urns (set partitions) Indistinguishable balls (unlabelled structures) Distinguishable urns (integer compositions) Indistinguishable urns (integer partitions) Constrained models Number of urns in surjections Number of parts in integer compositions Number of parts in integer partitions Bounded capacity in the DBDU model (hashing) Bounded capacity in the IBDU model (bosons) Stack polyominoes A problem in submarine detection The word counting problem The integer composition problem Fixing the number of boxes