by a more general quadratic algebra (possibly obtained by deformation) and then to derive Rq G] by requiring it to possess the latter as a comodule. A third principle is to focus attention on the tensor structure of the cat- egory of ( ; modules. This means of course just defining an algebra structure on Rq G]; but this is to be done in a very specific manner. Concretely the category is required to be braided and this forces (9.4.2) the existence...