However, the aforementioned line of work tackled subjectivity detection either as supervised or semi-supervised learning, requiring labelled data and extensive knowledge which are expensive to acquire.
both subjectivity and sentiment are context sensitive and in general quite domain dependent (Pang and Lee, 2008), so that classifiers trained on one domain often fail to produce satisfactory performance when shifted to new domains (Gamon et al., 2005;Blitzer et al., 2007).