The PLSA model (Hofmann, 1999) is a generative statistical latent class model: 1 , where The joint probability between a word and document, , is given by and using Bayes' rule can be written as: The likelihood function is given by  An important consideration in PLSA modeling is that the performance of the model is strongly affected by the initialization of the model prior to training.
a method for identifying a good initialization, or alternatively a good trained model, is needed.