For example, in several papers, frequently occurring noun phrases is used as the building block for detecting aspects (Hu and Liu, 2004a;Hu and Liu, 2004b;Ku et al., 2006).
for microblogs, frequency of a noun phrase alone is an insufficient indicator of an aspect, due to the inherent noise (unlike reviews, microblog posts are short and often not as focused) and redundancy (e.g., due to retweeting in the context of Twitter).