Modular System Basis

A basis of a Modular System $M$ is any set of Polynomials $B_1$, $B_2$, ...of $M$ such that every Polynomial of $M$ is expressible in the form

$$R_1B_1+R_2B_2+\ldots,$$

where $R_1$, $R_2$, ...are Polynomials.