One to Many?

[Geoffrey Hinton]

The boltzmann machine architecture allows one-to-many mappings
in an unkludgy way, and its a simple architecture.

If you insist on being deterministic, you can get BP to give a probability
distribution over a set of possible answers, provided each possible answer
has its own output unit.  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.

Geoff