I could not find any references for a basis-independent formulation of tensor networks: All papers I have found use pretty much (explicitly or implicitly) the canonical computational basis by defining tensors as lists of complex numbers.
While this is certainly ok from the perspective of "I want to compute stuff", it is not when trying to look at the bigger picture, i.e. realizing tensor networks as certain string diagrams in the category of finite dimensional Hilbert spaces.
Does anyone know of a resource that addresses this?