These relations are extracted from unstructured or semi-structured text using ontology learning from scratch (Velardi et al., 2013) and Open Information Extraction techniques (Etzioni et al., 2005;Yates et al., 2007;Wu and Weld, 2010;Fader et al., 2011;Moro and Navigli, 2013) which mainly stem from seminal work on is-a relation acquisition (Hearst, 1992) and subsequent developments (Girju et al., 2003;Pasca, 2004;Snow et al., 2004, among others).
these knowledge resources still lack semantic information about language units such as phrases and collocations.