  I ascribe the origin of Bloom-Gilman duality in DIS to a separation of scales
between the hard subprocess and soft resonance formation. The success of
duality indicates that the subprocesses of exclusive form factors are the same
as in DIS. The observed dominance of the longitudinal structure function at
large x in \pi N \to \mu^+\mu^- X can explain why local duality works for DIS
with a pion target. The failure of duality in semi-exclusive processes
indicates that high momentum transfer t is not sufficient to make the
corresponding subprocesses compact.
