Starting to write a z-push backend

Hi all,

I've been looking into this last afternoon and can't find a good tutorial for this.

There's this Linux-based groupware product I'm working on, and I want its addressbook to be automatically updated when a Windows Mobile device syncs with the PC.

I got Z-Push for this, and the sync between Windows Mobile and Ubuntu works nicely, seeing that VCard files get updated.

It seems that I now have to somehow write my own Z-Push backend class based on a Z-Push VCard backend class, but I don't understand what it interfaces with. Is there anybody here that can help me out with this? And am I tackling this problem from the right angle?

Cheers,
Wilmar.