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<Paper uid="C96-1081">
  <Title>Sjur NCrstebC/ Moshagen Computing Centre for the Humanities</Title>
  <Section position="3" start_page="0" end_page="478" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> Due to the complexity and wide coverage of lexical information, full-fledged lexicon systems easily grow undesirably big and must cope with intricate ~ nets of dependencies among lexical items.</Paragraph>
    <Paragraph position="1"> For keeping the speed of access at a satisfactory level, lexical information is often repeated in different entries to reduce the number of consultations needed for a single user query. This simplifies and speeds up the access of lexical information, but also blows up the size of the lexicon and leads to huge maintenance problems. In many cases, it also clutters the lexicon structure, so that important lexical relationships and generalizations are lost.</Paragraph>
    <Paragraph position="2"> Structuring the lexicon in inheritance hierarchies opens for more compact lexicon representations. So far, lexicons have been structured in syntactic inheritance hierarchies, in which more or less abstract syntactic classes form the upper nodes and actual words are associated with the leaf nodes (Flickinger and Nerbonne, 1992; Russell et al., 1992). However, the nature and number of these abstract syntactic classes are not very clear, and it seems difficult to come up with a sound method for how to decide on such classes.</Paragraph>
    <Paragraph position="3"> At the same time, there are also good reasons for assuming a similar hierarchy based on semantic properties (Hellan and Dimitrova-Vulchanova, 1994). Representing many competing hierarchies in the lexicon is a problem in itself and is here even more problematic as there are many complex relationships between semantic and syntactic properties (Gropen et al., 1992; Hellan and Dimitrova-Vulchanova, 1996).</Paragraph>
    <Paragraph position="4"> Another problem is related to the notions and structures adopted in the lexicon systems. Most lexicons today are constructed within the framework of some syntactic theory. This theory guides the structuring of lexical information and also decides what information should be available to the user (Andry et al., 1992; Flickinger and Nerbonne, 1992; Mel'Suk and Polgu~re, 1987; Russell et ~l., 1992; Krieger and Nerbonne, 1991). Some lexicon systems try to be reasonably theory-independent, though they still have to adopt some basic syntactic notions that locate them into a family of theories (Gofii and GonzAlez, 1995; Grimshaw and Jackendoff, 1985; Grishman et al., 1994).</Paragraph>
    <Paragraph position="5"> The Sign Expansion Approach forms a basis for creating non-redundant lexicon systems that are structured along semantic lines. The stored lexical entries are sign frames rather than actual words, and a whole system of expansion rules and consistency rules are used to generate dynamic entries of words that contain all the necessary semantic, syntactic, and morphological information.</Paragraph>
    <Paragraph position="6"> In Section 2, we give a brief introduction to a sign expansion theory called the Sign Model. Section 3 explains the use of lexical expansion rules, whereas some concluding remarks and directions for further work are found in Section 4.</Paragraph>
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  </Section>
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