  In this paper, we develop an iterative approach to span the whole set of
exotic matter models able to drive a traversable wormhole. The method, based on
a Taylor expansion of metric and stress-energy tensor components in a
neighbourhood of the wormhole throat, reduces the Einstein equations to an
infinite set of algebraic conditions, which can be satisfied order by order.
The approach easily allows the implementation of further conditions linking the
stress-energy tensor components among each other, like symmetry conditions or
equations of state. The method is then applied to some relevant examples of
exotic matter characterised by a constant energy density and that also show an
isotropic behaviour in the stress-energy tensor or obeying to a
quintessence-like equation of state.
