A systematic formalism is developed for the spin observables of the
ΔN→ΔN reaction, according to the polarization states
of
the four particles involved in the reaction. This formalism allows us
to
express all observables by means of a compact formula. Special
emphasis
is put on the search for relationships between different spin
observables.
A methodology is given for selecting a set of 39 observables, which
determines the 20 magnitudes of the amplitudes and 19 independent
relative phases between them.