sets of variables could be used for different decompositions of
problem space in subsets. Different studies I have drawn with my students
show that these decompositions are pertinent on the cognitive level. Their
elaboration relies on general observations drawn from different protocol
analysis. But they remain quasi-formal ones because they have nothing to do
with the analysis of protocol Olivier. I do not know if this is useful at
the level of supervisory control mechanism.

-------------------------------