Approximation of integration maps of vector measures and limit representations of Banach function spaces

We study whether or not the integration maps of vector measures can be computed as pointwise limits of their finite rank Radon Nikodym derivatives. The positive cases are obtained by using the circle of ideas related to the approximation property for Banach spaces. The negative ones are given by means of an appropriate use of the Daugavet property. As an application, we analyse when the norm in a space L-1(m) of integrable functions can be computed as a limit of the norms of the spaces of integrable functions with respect to the Radon-Nikodym derivatives of m.