A variety of NLP tasks, including inference, textual entailment (Glickman et al., 2005;Szpektor et al., 2008), and question answering (Moldovan et al., 1999), rely on semantic knowledge derived from term taxonomies and thesauri such as Word-Net.
the coverage of WordNet is still limited in many regions (even well-studied ones such as the concepts and instances below Animals and People), as noted by researchers such as  and (Hovy et al., 2009) who perform automated semantic class learning.