Simple basis functions (BFs).
A BF is the function determining the activation of a code
component in response to a given input. Minimizing
Because tends to make
unit activations decrease to zero it favors sparse codes.
But also favors a sparse hidden layer in the sense
that few hidden units contribute to producing the output.
's second term
Few separated basis functions. Hence FMS tries to figure out a way of using (1) as few BFs as possible for determining the activation of each output unit, while simultaneously (2) using the same BFs for determining the activations of as many output units as possible (common BFs). (1) and separate the BFs: the force towards simplicity (see ) prevents input information from being channelled through a single BF; the force towards few BFs per output makes them non-redundant. (1) and (2) cause few BFs to determine all outputs.
Summary. Collectively and (which make up ) encourage sparse codes based on few separated simple basis functions producing all outputs. Due to space limitations a more detailed analysis (e.g. linear output activation) had to be left to a TR  (on the WWW).