  Two complementary decoherence formalisms, Environment Induced Decoherence
(EID) for open systems and Self Induced Decoherence (SID) for close systems are
compared under a common General Theoretical Formalism for Decoherence (GTFD).
The differences and similarities of EID and SID are studied, e. g. that the
main difference is that EID only considers the relevant information of the
proper system S and neglects the rest, while SID considers all possible
information available from a certain class of measurement instruments and
neglects the non available information.
