Operator Identities, Representations of Algebras and the Problem of Normal Ordering

Families of operator identities appeared as a consequence of an existence of finite-dimensional representation of (super) Lie algebras of first-order differential operators and $q$-deformed (quantum) algebras of first-order finite-difference operators are presented. It is shown that those identities can be rewritten in terms of creation/annihilation operators and it leads to a simplification of the problem of the normal ordering in the second quantization method.