The published OCX Schema

The Vessel X coordinate system organised as a frame table or X-grid XGrid 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.
DistanceToAP	ocx	ocx:Quantity_T	req.	[1, 1]	False	If #0/FR0 (FR0 has per definition ReferenceLocation=0) is not located at AP, give the offset here (positive or negative distance).
XSpacingGroup	ocx	ocx:GridSpacingSystem_T	req.	[1, ∞]	False	The definition of a frame spacing group for a sequence of frame positions with equal spacing

XGrid has the following attributes:

Attribute	Namespace	Type	Use	Default	Description
isReversed	ocx	xs:boolean	opt.	false	true if the frame table is reversed with the origin at the fore of the vessel. The defaullt is false.
isMainSystem	ocx	xs:boolean	opt.	true	True if the FrameTable defines the main vessel grid. The default is true.
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.