 Let $K_0(\m V/X)$ be the relative Grothendieck group of varieties over $X\in Obj(\m V)$, with $\m V=\m V^{(qp)}_k$ (resp. $\m V=\m V^{an}_c$) the category of (quasi-projective) algebraic (resp. compact complex analytic) varieties over a base field $k$