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<Paper uid="P98-1046">
  <Title>Investigating regular sense extensions based on intersective Levin classes</Title>
  <Section position="7" start_page="297" end_page="298" type="concl">
    <SectionTitle>
5 Discussion
</SectionTitle>
    <Paragraph position="0"> We have presented a refinement of Levin classes, intersective classes, and discussed the potential for mapping them to WordNet senses. Whereas each WordNet synset is hierarchicalized according to only one aspect (e.g., Result, in the case of cut), Levin recognizes that verbs in a class may share many different semantic features, without designating one as primary. Intersective Levin sets partition these classes according to more coherent subsets of features (force, force+motion, force+separation), in effect highlighting a lattice of semantic features that determine the sense of a verb. Given the incompleteness of the list of members of Levin classes, each verb must be examined to see whether it exhibits all the alternations of a class. This might be approximated by automatically extracting the syntactic frames in which the verb occurs in corpus data, rather than manual analysis of each verb, as was done in this study.</Paragraph>
    <Paragraph position="1"> We have also examined a mapping between the English verbs that we have discussed and their Portuguese translations, which have several of the same properties as the corresponding verbs in English. Most of these verbs take the same alternations as in English and, by virtue of these alternations, achieve the same regular sense extensions.</Paragraph>
    <Paragraph position="2"> There are still many questions that require further investigation. First, since our experiment was based on a translation from English to Portuguese, we can expect that other verbs in Portuguese would share the same alternations, so the classes in Portuguese should by no means be considered complete. We will be using resources such as dictionaries and on-line corpora to investigate potential additional members of our classes. Second, since the translation mappings may often be many-to-many, the alterna- null tions may depend on which translation is chosen, potentially giving us different clusters, but it is uncertain to what extent this is a factor, and it also requires further investigation. In this experiment, we have tried to choose the Portuguese verb that is most closely related to the description of the English verb in the Levin class.</Paragraph>
    <Paragraph position="3"> We expect these cross-linguistic features to be useful for capturing translation generalizations between languages as discussed in the literature (Palmer and Rosenzweig, 1996), (Copestake and Sanfilippo, 1993), (Dorr, 1997). In pursuing this goal, we are currently implementing features for motion verbs in the English Tree-Adjoining Grammar, TAG (Bleam et al., 1998). TAGs have also been applied to Portuguese in previous work, resulting in a small Portuguese grammar (Kipper, 1994). We intend to extend this grammar, building a more robust TAG grammar for Portuguese, that will allow us to build an English/Portuguese transfer lexicon using these features.</Paragraph>
  </Section>
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