Let
I be a zero-dimensional ideal in a polynomial ring
F[s]:=F[s1,…,sn] over an arbitrary field
F. We show how to compute an
F-basis of the inverse system
I of
I. We describe the
F[s]-module
I by generators and relations and characterise the minimal length of a system of
F[s]-generators of
I. If the primary decomposition of
I is known, such a system can be computed. Finally we generalise the well-known notion of squarefree decomposition of a univariate polynomial to the case of zero-dimensional ideals in
F[s] and present an algorithm to compute this decomposition.