The paper aims at building a mathematical device, generalizing the polynomial approach in the control theory from time invariant systems to time varying ones. For that purpose, the algebraical rings are equipped with some operations more: the shift, the difference or the derivation. Based on that, the skew polynomials are defined which are non-commutative but satisfy a commutation equation.
93C05, 93B25, 93A99, 16S99, 16S36, 16W25, 16W20