Does Catias 3dxml format contain CAD as Nurbs, or is it just a triangulated/polygonal mesh?

I am curious if 3DXML is actually a Mesh or if it is Nurbs. Is it limited when compared to a Catpart/Catproduct assembly? My background is not Cad so apologies if this isn't a good question

The current version 4.3 of the 3D XML format has only support für polygons, but not nurbs. The specification of the format can be downloaded from the 3DS website. https://www.3ds.com/3ds-passport/downloads/