There can be exponential number of phrase sequence possible for each sentence of arbitrary length len(len = 1 for words; len > 1 for phrases) starting at an index st ∈ [0, We observed that most of opinion expression are centered around the head aspect thereby causing the space of potential opinion expressions to be quite sparse.
the thread on fine grained opinion expressions Choi et al., 2006;Breck et al., 2007) focus on subjective expression extraction which are generic instead of aspect specific.