1. A method of developing corner models for various classes of nonlinear systems, comprising the steps of: determining whether an explicit relationship between one or more performance targets vs. statistical model parameters is known; deciding, when an explicit relationship between one or more performance targets vs. statistical model parameters is known, whether the relationship is linear or nonlinear; constructing the relationship in a fractional form including a numerator and a denominator for the relationship, when an explicit relationship between one or more performance targets vs. statistical model parameters is not known; and decreasing the order of target functions or corner model equations on statistical model parameters.