Controls the constructive parameter space for spline curves and surfaces. Each knot sequence is
used for a dimension of the spline's parameter space. Thus, in a surface spline, there will be
two knot sequences, one for each parameter (u, v). The
ith, jth would be (ui,
vj), where the original knot sequences were (ui) and
(vj). Each knot of a spline curve or surface is described using a Knot.
The value of the parameter at the knot of the spline. The sequence of knots shall be a
nondecreasing sequence. That is, each knot's value in the sequence shall be equal to or
greater than the previous knot's value. The use of equal consecutive knots is normally
handled using the multiplicity.