such that the restriction of this mapping to the domain [0, 1]n for a fixed n is an n-ary
aggregation function f , with the convention F(x) = x for n = 1.
Aggregation functions are classed depending on their overall behavior in relation
to the inputs [17, 21, 22]. In some cases we require high inputs to compensate for
low inputs, or that inputs may average each other. In other situations, it may make
more sense that high scores reinforce each other and low inputs are essentially discarded.