  We revisit and extend the physical interpretation recently given to a certain
identity between large--deviations rate--functions (as well as applications of
this identity to Information Theory), as an instance of thermal equilibrium
between several physical systems that are brought into contact. Our new
interpretation, of mechanical equilibrium between these systems, is shown to
have several advantages relative to that of thermal equilibrium. This physical
point of view also provides a trigger to the development of certain alternative
representations of the rate--distortion function and channel capacity, which
are new to the best knowledge of the author.
