The task of taxonomy extraction is closely related to tasks such as hypernym detection (Hearst, 1992) or ontology learning (Buitelaar et al., 2005), in which a structured representation of concepts should be learned.
the task of taxonomy extraction does not have the formal nature 1 http://www.acm.org/publications/ class-2012 that either of these tasks in that the terms only need to be loosely associated.