Functor derivatives - a question and a result

Andre Joyal defined derivatives of analytic functors in his 1986 paper. Recently I heard the more general definition of a derivative F' of an endofunctor F defined via a universal sub-cartesian transformation from F'xId into F. Who is the author of this definition? The following result seems to indicate that outside of the realm of analytic functors derivatives may not be really useful: Theorem. Every non-faithful functor F:Set -> Set has the derivative F' = 0 (the constant functor to the empty set). xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx alternative e-mail address (in case reply key does not work): J.Adamek@tu-bs.de xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx