5. The method of claim 1 further comprising, training the Boltzmann machine to use the similarity in ranking the relevance.
7. The method of claim 5 wherein training the Boltzmann machine comprises selecting clusters for the machine, and building the Boltzmann machine with each document and each cluster corresponding to one unit of the Boltzmann machine, with each document unit corresponding to document features, and with edges between each document unit and each cluster unit representing a correlation between that document's relevancy and that cluster's relevancy.