problems about nurbs curve on EMC

hi, everybody~~I am back for some advice. these days I am trying to learn something about the nurbs algorithm in EMC. but unfortunately, there is little information on this subject. I really got help from John, BMG and DAN, and I really appreciated it. but as I moved forward, I got more questions. for example, I learned some thoery on nurbs curves, but I do not know how to make it available in EMC? maybe this is a tech-question. and simply I draw a curve in CAD, then I need to export the file to CAM to generate G code. is this proccess right??
then if this is the right proccess, then I wonder: my curve is based on spline curve, then CAM IS possible to generate G code based on "G1 G0 and G2/G3",SO this codes are able to use straight line and arcs to approximate the spline curve?? ---am I right?? but once again could you tell me is it possible to ask the CAM to generate codes that fit the spline? I mean to define new commands, like"G5.4 **",which is able to use spline to approximate my drawn curve.
I don't know if I had stated my question clearly, PLS help~~