 For an extensive development of the theory of channels sketched here, plus several explorations towards applications, see Barwise and Seligman (1997). See van Benthem (2000) for a study of conditions under which constraint satisfiability is preserved under infomorphisms, and Allo (2009) for an application of this framework to an analysis of the distinction between cognitive states and cognitive commodities. Finally, it must be mentioned that the notion of classification has been around for some years now in the literature, having being independently studied and introduced under names such as Chu spaces (Pratt 1995) or Formal Contexts (Ganter and Wille 1999). 