Information-preservation
is recognized as the only principle for probability-possibility transformation in
this work and the normalized transformation is the right method. This is based
on the viewpoint that the reason we can transfer probability and possibility is
that we believe the uncertainty being handled can be information-equivalently
described by both probability and possibility. That viewpoint is endorsed by
the random-fuzzy dual interpretation
of unknown uncertainty, which says that unknown uncertainty being estimated could be
interpreted as either randomness or fuzziness, depending on the available prior
information and the perspective of cognition and modeling. Information of uncertain
variable is defined in this work as its distribution. The suggested
information-preservation principle is different from Klir’s principle, which is
in fact an entropy-preservation principle. Then we investigated the problem of
information preservation and propagation in parallel probability-possibility
systems. By parallel, we mean the two uncertainty systems have the same priori
information. After uncertainty propagation the two parallel systems will
generally bifurcate, which means information preservation only holds locally
between the two parallel systems. This observation accords with our intuition
since probability and possibility use different normalizations as well as different
disjunctive operators, which makes them two different uncertainty systems
appropriate for randomness and fuzziness, respectively.