The published OCX Schema

Abstract base class for any 3D curve. Curve3D has the following child elements:

Child	Namespace	Type	Use	Cardinality	Choice	Description
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.
Length	ocx	ocx:Quantity_T	opt.	[0, 1]	False	The curve length computed by the sending application. Used to verify geometry reconstruction.

Curve3D 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.