In contrast, the unsupervised approaches do not depend on training sets but
instead use techniques to utilise the information provided in the applied corpus (e.g.
word collocation, keywords and part-of-speech). These approaches can further be
divided into knowledge-based and knowledge-poor approaches (Navigli, 2009). The
former approaches use external knowledge resources (i.e. knowledge model, thesaurus,
taxonomy) while the latter do not depend on external resources (i.e. statistics).