Approximation of choice function

For approximation of choice functions by “good”, e. g. simpler or better known, choice functions, the upper and lower approximations are defined and criteria are established for a class of functions which can be approximated in a specific class of “good” functions. For the classes of functions described by characteristic conditions, conventional in the choice theory and regarded as approximating, a class of approximating functions is defined and formula are given for design of the approximating: function.