  We present the most general parametrisation of models of dark energy in the
form of a scalar field which is explicitly coupled to dark matter. We follow
and extend the Parameterized Post-Friedmannian approach, previously applied to
modified gravity theories, in order to include interacting dark energy. We
demonstrate its use through a number of worked examples and show how the
initially large parameter space of free functions can be significantly reduced
and constrained to include only a few non-zero coefficients. This paves the way
for a model-independent approach to classify and test interacting dark energy
theories.
