Using SDRT as a formal framework, we have the following discourse relations: Contrast(a,b) in (1) marked by although, Continuation(a,b) in (2) marked by and, and Attribution(a,b) in (4).We observe in our corpus that segments related by a Contrast or Continuation relation often share the same subjective orientation (about 80 %).
discourse connectors are not the only indicator for deciding whether a segment is opinionated or not.