predicate fzn_disjunctive_strict_opt(array[int] of var opt int: s,
                                     array[int] of var int: d) =
        forall (i in index_set(d)) (d[i] >= 0) /\
        forall (i,j in index_set(d) where i<j) (
          absent(s[i]) \/ absent(s[j]) \/
          deopt(s[i])+d[i] <= deopt(s[j]) \/
          deopt(s[j])+d[j] <= deopt(s[i])
        );