[Haskell-cafe] Looking for lost library

Hi, Sorry for stupid question, but... Some time ago I read a beautiful paper about variables that had their dependencies automatically tracked and could trigger recalculation when changed. Prototype was implemented in OCaml, then reimplemented in Haskell (using monads). I would like to read that paper once again, but... I lost it :( I do not remember neither title, nor authors. Google asked about any keywords that come to my mind do not show any interesting results. So I ask here :) Can anybody help me, please? Thanks for any pointers... -- Gracjan