There has been great interest in unsupervised learning among NLP researchers due to the availability of large amounts of unprocessed text through the Web, newswire providers, scientific repositories and other sources in contrast to the onerous requirements of creating task-specific manually annotated data for training supervised analysers.
relevant to our work is the field of topic modelling, where Bayesian latent-variable models are used to induce meaningful generalisations from observations of co-occurrences.