Given the following Bayessian Network:
I wonder when is it reasonable to estimate $p(u\mid c)$ as
$$ p(u\mid c) \approx p(c\mid w=w_1,\ldots,w_t)$$
I want to estimate that because I can't calculate $p(u\mid c)$ because $u$ is not observable. I've been looking for inference and reasoning in bayes networks but I couldn't find any inference like this.