They both use three linearchain CRF layers for the three different prediction tasks: CRF-RA is for task t a ; CRF-RO is for task t o ; CRF-M is for task t m .
we mine aspect and opinion term extraction rules that are mainly based on the dependency relations between words, since their effectiveness has been validated by existing rule based approaches (Zhuang et al., 2006;Qiu et al., 2011).