  I review the formalism of classical extensions of quantum mechanics
introduced by Beltrametti and Bugajski, and compare it to the classical
representations discussed e.g. by Busch, Hellwig and Stulpe and recently used
by Fuchs in his discussion of quantum mechanics in terms of standard quantum
measurements. I treat the problem of finding Bayesian analogues of the state
transition associated with measurement in the canonical classical extension as
well as in the related 'uniform' classical representation. In the classical
extension, the analogy is extremely good.
