One to Many?

[Stephen J. Hanson]

....  Unlike the Boltzmann machine, BP cannot represent
probabilites of combinations of output units.  For example, a Boltzmann
machine can give high probability to  the output vectors 01 and 10 and low
probability to 11 and 00.  BP cannot do this.
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However, this is just the sort of thing one can do with
multiple hidden layers, in which the next hidden layer is
making (certainty/uncertainty) decisions about combinations of <output> units 
below....of course with the caveat that learning time
increases and learning efficacy decreases...comparatively
BMs take a bit of training time as well..

	Steve (jose at bellcore.com)