Descent and generic forms via symmetric monoidal categories

Let A be any algebra, perhaps with some extra structure, of finite dimension over a field K of characteristic zero. (Examples for extra structure: a Hopf algebra, a comodule algebra).

Consider the following question:
Over what subfields of K is A defined, and in what ways? (Or in other words: over which subfields of K does A admit a form, and what are these forms?).
In this talk I will present a new approach to this problem.
I will explain a construction of a symmetric monoidal category C_A.
The construction of this category will give rise to a subfield K_0 of K, such that if A has a form over K_1, then K_0 is contained in K_1. 
I will explain how can one use Deligne's Theory on symmetric monoidal categories to construct a ``generic form'' of A, that is- a form over a commutative ring B (which is a K_0 algebra), such that every form of A is given by a specialization of B. 

If time permits, I will also describe some applications in the theory of finite dimensional semisimple Hopf algebras.