j
       1   0
      -------
  1  | a | b |
i     -------
  0  | c | d |
      -------
a = number of variables on which both objects i and j are 1
b = number of variables where object i is 1 and j is 0
c = number of variables where object i is 0 and j is 1
d = number of variables where both i and j are 0
a+b+c+d = p, the nubmer of variables.