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<Paper uid="I05-2036">
  <Title>Svetlana.Hensman@comp.dit.ie</Title>
  <Section position="8" start_page="212" end_page="213" type="concl">
    <SectionTitle>
7 Conclusions
</SectionTitle>
    <Paragraph position="0"> In this paper we have described an approach for constructing conceptual graphs for English sentences, using VerbNet, WordNet and some domain-specific knowledge. The achieved accu- null racy is strongly influenced by the lack of VerbNet descriptions of many verbs present in both corpora, as well as the lack of semantic frames for the present verb sense. Also, as the approach is not statistical, it does not require large amount of training data.</Paragraph>
    <Paragraph position="1"> There are several other lexical resources currently available that seem suitable for semantic role identification, among them FrameNet and PropBank. Our choice of VerbNet as a lexical resource is based on our belief that a set of domain-independent descriptive role labels (such as those defined in VerbNet) is more suitable as it allows for generalisations.</Paragraph>
    <Paragraph position="2"> A drawback of both FrameNet and PropBank is that the roles do not include any selectional restrictions, which makes it hard for a non-statistical method to identify the correct filler for each role. As shown earlier, the selectional restrictions defined for the semantic roles prove to be a valuable asset when deciding if a phrase can be a role filler. While we can resolve the majority of them by analysing the syntactic structure or by using the WordNet hierarchy, some are more difficult to resolve. For example, the restriction solid describes an attribute or a state of an object, relations which cannot be checked by using WordNet. FrameNet on the other hand defines usages not only for verbs, but also for nouns. As one of the causes for the relatively poor performance of the conceptual graph building module is the lack of a sufficient number of relation-correction rules, our current approach to increasing their number is trying to extract the rules from FrameNet.</Paragraph>
    <Paragraph position="3"> Work on the system is ongoing and efforts are continuing to implement a verb sense disambiguation component.</Paragraph>
  </Section>
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