  Micro-Macro Duality means here the universal mutual relations between the
microscopic quantum world and various macroscopic classical levels, which can
be formulated mathematically as categorical adjunctions. It underlies a unified
scheme for generalized sectors based upon selection criteria proposed by myself
in 2003 to control different branches of physics from a unified viewpoint,
which has played essential roles in extending the Doplicher-Haag-Roberts
superselection theory to various situations with spontaneously as well as
explicitly broken symmetries.
  Along this line of thought, the state correlations between a system and a
measuring apparatus necessary for measurements can canonically be formulated
within the context of group duality; the obtained measurement scheme is not
restricted to the quantum mechanical situations with finite number of particles
but can safely be applied to quantum field theory with infinite degrees of
freedom whose local subalgebras are given by type III von Neumann algebras.
