On representation of $k$-valued logic functions by a sum of products of subfunctions

The set of variables of a $k$-valued logic function $f(x_1,\dots,x_n)$ is partitioned into $t$ parts, $t>1$, and a polynomial representation of the function $f$ is considered where the terms are products of all possible subfunctions corresponding to the partitioning. We analyse conditions under which an arbitrary function admits a representation in such a polynomial form.