The constraints mean that the ratio of "virtual output" vs. "virtual input"
should not exceed 1 for every DMU. The objective is to obtain weights (vi) and
(ur) that maximize the ratio of DMUo, the DMU being evaluated. By virtue
of the constraints, the optimal objective value 6* is at most 1. Mathematically,
the nonnegativity constraint (2.5) is not sufficient for the fractional terms in
(2.4) to have a positive value. We do not treat this assumption in explicit
mathematical form at this time. Instead we put this in managerial terms by
assuming that all outputs and inputs have some nonzero worth and this is to
be reflected in the weights Ur and Vi being assigned some positive value.