Fine-grained opinion analysis methods often make use of linguistic features but typically do not take the interaction between opinions into account. This article describes a set of experiments that demonstrate that relational features, mainly derived from dependency-syntactic and semantic role structures, can significantly improve the performance of automatic systems for a number of fine-grained opinion analysis tasks: marking up opinion expressions, finding opinion holders, and determining the polarities of opinion expressions. These features make it possible to model the way opinions expressed in natural-language discourse interact in a sentence over arbitrary distances. The use of relations requires us to consider multiple opinions simultaneously, which makes the search for the optimal analysis intractable. However, a reranker can be used as a sufficiently accurate and efficient approximation. A number of feature sets and machine learning approaches for the rerankers are evaluated. For the task of opinion expression extraction, the best model shows a 10-point absolute improvement in soft recall on the MPQA corpus over a conventional sequence labeler based on local contextual features, while precision decreases only slightly. Significant improvements are also seen for the extended tasks where holders and polarities are considered: 10 and 7 points in recall, respectively. In addition, the systems outperform previously published results for unlabeled (6 F-measure points) and polarity-labeled (10–15 points) opinion expression extraction. Finally, as an extrinsic evaluation, the extracted MPQA-style opinion expressions are used in practical opinion mining tasks. In all scenarios considered, the machine learning features derived from the opinion expressions lead to statistically significant improvements.
Titolo: | Relational Features in Fine-grained Opinion Analysis |
Autori: | R. Johansson; A. Moschitti |
Autori Unitn: | |
Titolo del periodico: | COMPUTATIONAL LINGUISTICS |
Anno di pubblicazione: | 2013 |
Numero e parte del fascicolo: | 3 |
Codice identificativo Scopus: | 2-s2.0-84881192667 |
Codice identificativo ISI: | WOS:000325864800002 |
Digital Object Identifier (DOI): | http://dx.doi.org/10.1162/COLI_a_00141 |
Handle: | http://hdl.handle.net/11572/95142 |
Appare nelle tipologie: | 03.1 Articolo su rivista (Journal article) |