Monotone Boolean functions (mbfs)
defn mbf f: a mapping X -> {0,1} such that x <= y implies f(x) <= f(y) forall x, y in X
X = {0,1}3 f = x1 OR x2x3 LU(f) = {100,011} UZ(f) = {010,001}
a mbf f is uniquely defined by its border points: lower units LU = {x*: f(x) < f(x*) forall x in X} upper zeros UZ = {x*: f(x) > f(x*) forall x in X)