Hello, I think the above book by Reyes, Reyes and Zolfaghari is quite intriguing. At the same time I can't get my mind around the notions of "generic figures" and "change of figures"! The first seems to be objects in the base category and the latter morphisms in the base category. Whoever has read this book and understands it please give me some pointers. Sorry the vague call for help. Kind regards, Vasili