Table 2.

The type of factor interaction expression

Formula	Interaction
q(x, y) < Min(q(x),q(y))	Weaken, nonlinear
Min(q(x), q(y)) < q(x, y) < Max(q(x),q(y))	Weaken, unilateral
q(x, y) > Max(q(x),q(y))	Enhance, bi-linear
q(x, y) = q(x) + q(y)	Independent
q(x, y) > q(x) + q(y)	Enhance, nonlinear