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<Paper uid="P06-2063">
  <Title>Automatic Identification of Pro and Con Reasons in Online Reviews</Title>
  <Section position="4" start_page="483" end_page="483" type="intro">
    <SectionTitle>
2 Pros and Cons in Online Reviews
</SectionTitle>
    <Paragraph position="0"> This section describes how we define reasons in online reviews for our study. First, we take a look at how researchers in Computational Linguistics define an opinion for their studies. It is difficult to define what an opinion means in a computational model because of the difficulty of determining the unit of an opinion. In general, researchers study opinion at three different levels: word level, sentence level, and document level.</Paragraph>
    <Paragraph position="1"> Word level opinion analysis includes word sentiment classification, which views single lexical items (such as good or bad) as sentiment carriers, allowing one to classify words into positive and negative semantic categories. Studies in sentence level opinion regard the sentence as a minimum unit of opinion. Researchers try to identify opinion-bearing sentences, classify their sentiment, and identify opinion holders and topics of opinion sentences. Document level opinion analysis has been mostly applied to review classification, in which a whole document written for a review is judged as carrying either positive or negative sentiment. Many researchers, however, consider a whole document as the unit of an opinion to be too coarse.</Paragraph>
    <Paragraph position="2"> In our study, we take the approach that a review text has a main opinion (recommendation or not) about a given product, but also includes various reasons for recommendation or nonrecommendation, which are valuable to identify. Therefore, we focus on detecting those reasons in online product review. We also assume that reasons in a review are closely related to pros and cons expressed in the review. Pros in a product review are sentences that describe reasons why an author of the review likes the product. Cons are reasons why the author doesn't like the product. Based on our observation in online reviews, most reviews have both pros and cons even if sometimes one of them dominates.</Paragraph>
  </Section>
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