Data Reduction - polynomial SISL Curve, Points, or Points and Tangents as Input
To compute the approximation to the data given by points, or points and derivatives (tangents), and represent it as a SISL curve. The approximation is determined by first forming the cubic interpolant to the data, and then performing knot removal on this initial approximation.

Degree Reduction - polynomial SISL Curve as Input
To approximate the input SISL curve by a cubic SISL curve with error less than the desired accuracy in each component.

Data Reduction - polynomial SISL Surface, Points, or Points and Tangents as Input
To remove knots from a polynomial tensor product SISL surface and calculate an approximation to the original surface on the reduced knot vectors. Or to compute a polynomial tensor product SISL surface approximation of specified order to the given rectangular array of points. Or to compute a bicubic Hermite SISL surface approximation to the positions and derivatives given.

Degree Reduction - polynomial SISL Surface as Input
To compute a cubic polynomial tensor product SISL surface approximation to a given tensor product SISL surface of arbitrary order, with error less than a specified acceptable deviation in each component.