Using lexical level information in discourse structures for Basque sentiment analysis

摘要

Systems for opinion and sentiment analysis rely on different resources: a lexicon, annotated corpora and constraints (morphological, syntactic or discursive), depending on the nature of the language or text type. In this respect, Basque is a language with fewer linguistic resources and tools than other languages, like English or Spanish. The aim of this work is to study whether some kinds of discourse structures based on nuclearity are sufficient to correctly assign positive and negative polarity with a lexicon-based approach for sentiment analysis. The evaluation is performed in two phases: i) Text extraction following some constraints on discourse structure from manually annotated trees, ii) Automatic annotation of semantic orientation (or polarity). Results show that the method is useful to detect all positive cases, but fails with the negative ones. An error analysis shows that negative cases have to be addressed in a different way. The immediate results of this work include an evaluation on how discourse structure can be exploited in Basque. In the future, we will also publish a manually created Basque dictionary to use in sentiment analysis tasks.