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<Paper uid="E89-1000">
  <Title>Current Issues in Computational Lexical Semantics</Title>
  <Section position="3" start_page="264" end_page="264" type="intro">
    <SectionTitle>
1. Introduction
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    <Paragraph position="0"> I believe we have reached an interesting turning point in research, where linguistic studies can be informed by computational tools for lexicology as well as an appreciation of the computational complexity of large lexical databases. Likewise, computational research can profit from an awareness of the grammatical and syntactic distinctions of lexical items; natural language processing systems must account for these differences in their lexicons and grammars. The wedding of these disciplines is so important, in fact, that I believe it will soon be impossible to carry out serious computational research in our field without the help of electronic dictionaries and computational lexicographic resources \[Walker, 1986\]. Positioned at the center of this synthesis is the study of word meaning, lexical semantics, which is currently witnessing a minor revival.</Paragraph>
    <Paragraph position="1"> Given this, I would like to turn to a few issues that I feel the lexical semantics community should  address. In particular, I will pose the following four questions: 1. Has recent work in lexical semantics been methodologically any sounder than the previous work in the field? 2. Do theories being developed today have any broader coverage than the earlier descriptive work? 3. Do current theories provide any new insights into the representation of knowledge for the global structure of the lexicon? 4. Finally, has recent work provided the computational community with useful resources for parsing, generation, and translation research?  Before answering these questions, I would like to establish two points that will figure prominently in our critique of the field. The first is that, without an appreciation of the syntactic structure of a language, the study of lexical semantics is bound to fail. There is no way in which meaning can be completely divorced from the structure that carries it. This is more a methodological point than anything else, since grammatical distinctions are a useful metric in evaluating competing semantic theories.</Paragraph>
    <Paragraph position="2"> c~--, - xvii The second point is that the meanings of words should somehow reflect the deeper, conceptual structures in the system and the domain it operates in. This is tantamount to stating that the semantics of natural language should be the image of (nonlinguistic) conceptual organizing principles (whatever their structure).</Paragraph>
    <Paragraph position="3"> Some of the major points I would like to make here are the following. First, a clear notion of semantic well-formedness will be necessary in order to characterize a theory of possible word meaning. This may entail idealizing the notion of lexical meaning away from other semantic influences. For instance, this might suggest that discourse and pragmatic factors should be handled differently or separately from the semantic contributions of lexical items in composition (contra \[Hobbs, 1987\]. Although this is not a necessary assumption and may in fact be wrong, it may help narrow our focus on what is important for lexical semantic descriptions.</Paragraph>
    <Paragraph position="4"> Secondly, lexical semantics must look for representations that are richer than thematic role descriptions \[Fillmore, 1968\]. As argued in \[Levin and Rappaport, 1986\], named roles are useful, at best, for establishing fairly general mapping strategies to the syntactic structures in language. The distinctions possible with &amp;quot;theta&amp;quot; roles are much too coarse-grained to provide a useful semantic interpretation of a sentence. What is needed, therefore, is a principled method of lexical decomposition. This presupposes, if it is to work at all, (1) a rich, recursive theory of semantic composition, (2) the notion of semantic well-formedness mentioned above, and (3) an appeal to levels of interpretation in the semantics \[Scha, 1983\].</Paragraph>
    <Paragraph position="5"> Thirdly, and related to the point above, the lexicon is not just verbs. Recent work has done much to clarify the nature of verb classes and the syntactic constructions that each allows \[Levin, 1985\]. Yet it is not clear whether we are any closer to understanding the underlying nature of verb meaning, why the classes develop as they do, and what consequences these distinctions have for the rest of the lexicon and grammar. The curious thing is that there has been little attention paid to the other lexical categories (but see \[Fass, 1988\]. That is, we have little insight into the semantic nature of adjectival predication, and even less into the semantics of nominals. Not until all major categories have been studied can we hope to arrive at a balanced understanding of the lexicon and the methods of composition.</Paragraph>
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