Quantitative measures are determined for the evaluation of the structural properties of nonlinear processes. These include simple structural measures for the evaluation of the "best" achievable control quality in a given process, regardless of the type of the controller being used. The notions of relative orders (time delays) with respect to manipulated inputs and disturbances and characteristic matrix are used to determine the best achievable closed-loop response for each controlled output and to derive the conditions under which the best closed-loop response in all outputs together with complete input-output decoupling is feasible.