In work by Wiebe, Bruce, and O'Hara (Wiebe et al., 1999;Bruce and Wiebe, 2000), a corpus of 1,001 sentences 3 of the Wall Street Journal TreeBank Corpus (Marcus et al., 1993) was manually annotated with subjectivity classifications.
each sentence was assigned a subjective or objective classification, according to concensus tags derived by a statistical analysis of the classes assigned by three human judges (see (Wiebe et al., 1999) for further information).