Strongly internal sets and generalized smooth functions
  Based on a refinement of the notion of internal sets in Colombeau's theory, so-called strongly internal sets, we introduce the space of generalized smooth functions, a maximal extension of Colombeau generalized functions. Generalized smooth functions as morphisms between sets of generalized points form a sub-category of the category of topological spaces. In particular, they can be composed unrestrictedly. 
Paolo Giordano, Michael Kunzinger, Hans Vernaeve
math.FA