4. Appendix: direct handling, Norman loop

The cognitive aspects of a human's approach to interacting with the environment have been modeled by various authors, most notably Norman in 1986 [2] . His work is known as action theory. It provides a framework for interpreting most of the phenomena involved in human-machine interaction. In particular, this model introduces the notions of distances perceived by the user when interacting with a machine: semantic distance, articulatory distance and operative distance (figure 5 ).