From the very beginning, the ETS framework has been
inspired by the
formal/esthetical beauty and power of a dynamic (and generalized) version of the generative grammar
model:
to support an evolving concept of
class, one needs an evolving set of transformations that
captures the class description and also modifies
the corresponding (evolving)
mathematical structure on the representation “space”.
(In that sense, if besides
ETS there is another formal realization of this vision, it should definitely be investigated.)