  In this paper, we emphasize that a UV SUSY-breaking theory can be realized
either linearly or nonlinearly. Both realizations form the dual descriptions of
the UV SUSY-breaking theory. Guided by this observation, we find subtle
identities involving the Goldstino field and matter fields in the standard
nonlinear realization from trivial ones in the linear realization. Rather
complicated integrands in the standard nonlinear realization are identified as
total-divergences. Especially, identities only involving the Goldstino field
reveal the self-consistency of the Grassmann algebra. As an application of
these identities, we prove that the nonlinear Kahler potential without or with
gauge interactions is unique, if the corresponding linear one is fixed. Our
identities pick out the total-divergence terms and guarantee this uniqueness.
