Parameter estimation for this model can be done by maximizing a lower bound E(φ, θ) on the loglikelihood of the data derived by application of Jensen's inequality: 2 (3) These latent rationales approach the first objective, namely, uncovering which parts of the input text contribute towards a decision.
note that an NN controls the Bernoulli parameters, thus nothing prevents this NN from selecting the whole of the input, thus defaulting to a standard text classifier.