# Singular

## C.1 Standard bases

### Definition

Let and let be a submodule of . Note that for r=1 this means that is an ideal in . Denote by the submodule of generated by the leading terms of elements of , i.e. by . Then is called a standard basis of if generate .

A standard basis is minimal if .

A minimal standard basis is completely reduced if

### Properties

normal form:
A function , is called a normal form if for any and any standard basis the following holds: if then does not divide for all . The function may also be applied to any generating set of an ideal: the result is then not uniquely defined.

is called a normal form of with respect to

ideal membership:
For a standard basis of the following holds: if and only if .
Hilbert function:
Let be a homogeneous module, then the Hilbert function of (see below) and the Hilbert function of the leading module coincide, i.e., .