This question is more of a graph problem. Suppose $A=\{1,2,..,n\}$, and we want to construct the sets $B(i)$,$1\leq i\leq n$, such that $i \not\in B(i)$ and the following constraints on the set $B(i)$ are satisfied: 1) If $j \in B(i)$ then $ i \notin B(j)$, 2) For all $i \in B(j)$, $B(j) \setminus \{i\} \not \subset B(i)$, 3) For all $i \notin B(k)$, $B(i) \not \subset {\{k\} \cup B(k)}$ Can we construct such subsets for all values of $n$? I can construct such subsets for $n=4,5,6$, but I can not generalize this method of construction for all values of $n$. I believe that such subsets can not be constructed in general.