1. Adequacy arrow direction: If A is a sufficient condition for B, then the arrow points from A to B, represented as A → B. This means that when A is established, B must also be established, but the establishment of B does not necessarily require the establishment of A.
2. Necessity arrow direction: If A is a necessary condition for B, then the arrow points from B to A, represented as B → A. This means that the establishment of B must be based on the establishment of A, but the establishment of A does not necessarily lead to the establishment of B.
3. Sufficient and Necessary Arrow Direction: If A is both a sufficient condition for B and a necessary condition for B, then the arrow can represent both directions, that is, A? B. This means that A and B are equivalent, if A holds, then B must hold, and if B holds, then A must also hold.