qof<something> vs gnc<something> functions ?

[Geert Janssens]

I was looking into this bug that seemed a fairly trivial to fix:
https://bugzilla.gnome.org/show_bug.cgi?id=343727

That is, if some consensus can be reached on what type the currency should be 
from a qof point of view. The op proposed QOF_TYPE_STRING, although Derek 
wasn't fully convinced. And in the end Phil also thought a currency type would 
be better. The bug has been sleeping since.

Personally, I don't know enough about qof or gnc to make a decision. I'm 
bringing this up because the bug got me confused: it more or less reveals of 
two different 'interfaces' to the gnucash data: you can access it via qof or 
via gnc_xxx_yyy. But I don't understand the difference (if any) between the 
two.

I also notice that there are gncXYZRegister functions that are used to link a 
certain parameters with a getter and setter function. These getter/setter 
functions are in most cases gncSometing and very sometimes they are 
qofSomething.

So what's the relationship between the qofABC and gncDEF type of functions ?

Geert