The published OCX Schema

Non-Uniform Rational Spline Base curve definition. NURBS3D has the following child elements:

Child	Namespace	Type	Use	Cardinality	Choice	Description
ControlPtList	ocx	ocx:ControlPtList_T	req.	[1, 1]	False	List of control points (X,Y,Z) and their optional weights. The array length N=degree+1. A minimum of 2 control points is necessary to define a curve.
Description	ocx	xs:string	opt.	[0, 1]	False	Contains a description of the component its parent represents. The description is stored as a string. You can use this element for whatever purposes you require. This element can be used inside many OCX XML elements but is optional.
KnotVector	ocx	ocx:KnotVector_T	req.	[1, 1]	False	The knot-vector is a list of size m=+n-1 knots where p is the polynomial basis degree and n is the number of control points. The knot vector consists of a non-decreasing sequence of values. Knot multiplicities can be included. A knot multiplicity means that a knot value can be repeated up to p+1 times.
Length	ocx	ocx:Quantity_T	opt.	[0, 1]	False	The curve length computed by the sending application. Used to verify geometry reconstruction.
NURBSproperties	ocx	ocx:NURBSProperties_T	req.	[1, 1]	False	Properties of the basis functions in surface V direction.

NURBS3D has the following attributes:

Attribute	Namespace	Type	Use	Default	Description
is2D	ocx	xs:boolean	opt.	false	Set to True if the Curve3D is given in 2D space.
GUIDRef	ocx	Restriction of type ocx:guid	opt.		A globally unique ID referring to an entity in the authoring application. The sending application creates and holds the GUID. Used to establish a unique reference to an entity persistent between applications.
name	ocx	xs:string	opt.		An optional descriptive or display name.
id	ocx	xs:ID	req.		An identifier for an element unique within the scope of the XML file. Each id must be unique within a document. The attribute uses the standard XML 1.0 ID type as defined in the XML Schema specification. This attribute is required in many OCX XML elements and an application should generate them automatically.