The work of Hatzivassiloglou and McKeown in 1997 (1997) consists in using the coordinating conjunctions present between a word already classified and an unclassified word, followed by the contributions of researcher Nasukawa and his team in 2003 (2003) who proposed a new method for extracting associated concepts from segments and summing the orientations of the opinion vocabulary present in the same segment.
In the same year, researchers Yu and Hatzivassiloglou (2003) used the probability of ranking a word to measure the strength of the orientation of the named entities. In 2006, researchers Kanayama and Nasukawa (2006) as well as Ding and Liu (2008) in 2008 proposed, for their part, a learning-based approach that uses the coordination conjunctions present between a word already classified and a word unclassified.