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<Paper uid="P02-1041">
  <Title>Coupling CCG and Hybrid Logic Dependency Semantics</Title>
  <Section position="9" start_page="11" end_page="11" type="concl">
    <SectionTitle>
6 Conclusions and Future Work
</SectionTitle>
    <Paragraph position="0"> Since it is couched in hybrid logic, HLDS is ideally suited to be logically engineered to the task at hand. Hybrid logic can be made to do exactly what we want, answering to the linguistic intuitions we want to formalize without yielding its core assets - a rich propositional ontology, decidability, and favorable computational complexity.</Paragraph>
    <Paragraph position="1"> Various aspects of meaning, like dependency relations, contextual reference, tense and aspect, and information structure can be perspicuously encoded with HLDS, and the resulting representations can be built compositionally using CCG. CCG has close affinities with dependency grammar, and it provides a competitive and explanatorily adequate basis for a variety of phenomena ranging from coordination and unbounded dependencies to information structure. Nonetheless, the approach we describe could in principle be fit into other unification-based frameworks like Head-Driven Phrase Structure Grammar.</Paragraph>
    <Paragraph position="2"> Hybrid logic's utility does not stop with sentential meaning. It can also be used to model discourse interpretation and is closely related to logics for knowledge representation. This way we can cover the track from grammar to discourse with a single meaning formalism. We do not need to translate or make simplifying assumptions for different processing modules to communicate, and we can freely include and use information across different levels of meaning.</Paragraph>
    <Paragraph position="3"> We have implemented a (preliminary) Java package for creating and manipulating hybrid logic terms and connected it to Grok, a CCG parsing system.</Paragraph>
    <Paragraph position="4">  The use of HLDS has made it possible to improve  The software is available athttp://opennlp.sf.net and http://grok.sf.netunder an open source license.</Paragraph>
    <Paragraph position="5"> the representation of the lexicon. Hybrid logic nominals provide a convenient and intuitive manner of localizing parts of a semantic structure, which has made it possible to greatly simplify the use of inheritance in the lexicon. Logical forms are created as an accumulation of different levels in the hierarchy including morphological information. This is particularly important since the system does not otherwise support typed feature structures with inheritance.</Paragraph>
    <Paragraph position="6"> Hybrid logics provide a perspicuous logical language for representing structures in temporal logic, description logic, AVMs, and indeed any relational structure. Terms of HLDS can thus be marshalled into terms of these other representations with the potential of taking advantage of tools developed for them or providing input to modules expecting them.</Paragraph>
    <Paragraph position="7"> In future work, we intend to combine techniques for building wide-coverage statistical parsers for CCG (Hockenmaier and Steedman, 2002; Clark et al., 2002) with corpora that have explicitly marked semantic dependency relations (such as the Prague Dependency Treebank and NEGRA) to produce HLDS terms as the parse output.</Paragraph>
  </Section>
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