Opinion mining tasks
At the document (or review) level:
Task: sentiment classification of reviews
Classes: positive, negative, and neutral
Assumption: each document (or review) focuses on a single object (not true in many discussion posts) and contains opinion from a single opinion holder.
At the sentence level:
Task 1: identifying subjective/opinionated sentences
Classes: objective and subjective (opinionated)
Task 2: sentiment classification of sentences
Classes: positive, negative and neutral.
Assumption: a sentence contains only one opinion
not true in many cases.
Then we can also consider clauses or phrases.