We can use non-uniform sparse Dirichlet priors on the probabilities of these rules to encourage "topic stickiness".
by setting the Dirichlet parameters for the "topic shift" rules Doc j,i → Doc j,i Topic i where i = i much lower than the parameters for the "topic preservation" rules Doc j,i → Doc j,i Topic i , Bayesian inference will be biased to find distributions in which adjacent words will tend to have the same topic.