In extractive approaches, which are usually applicable in text and ontology summarization (Jones, 2007) (Zhang et al., 2007), a set of features is extracted directly from the input data.
in non-extractive methods, which generally are employed in graph (Navlakha et al., 2008) and database (Bu et al., 2005) summarization, new sentences from the input data are generated (Hahn and Mani, 2000) to form a summary.