<?xml version="1.0" standalone="yes"?>
<Paper uid="W00-1102">
  <Title>Exploiting Lexical Expansions and Boolean Compositions for Web Querying</Title>
  <Section position="6" start_page="19" end_page="20" type="concl">
    <SectionTitle>
Conclusion
</SectionTitle>
    <Paragraph position="0"> A comparative experiment among three search strategies has been carried out with the aim of estimating the benefits of lexical expansions and * of composition strategies over the basic keywords of a query. Results lead us believe that search strategies that combine a number of linguistic optirnizations with a proper Boolean composition can improve the performance of an existing search engine on the web. In particular given KAS (no expansions, with AND composition search) as baseline, KIS (expansion insertion search) performs better but one case (i.e. with expansions greater than 3) and KCS (Cartesian composition search) performs better than KIS. Furthermore, KCS has a maximum performance, with expansions equal to 2 or 3, significantly higher than KIS, probably because KCS retrieves web documents that are not retrieved by K/S, which basically reearranges the order of KAS documents.</Paragraph>
    <Paragraph position="1"> At present we still have no clear data to determine which number and which kind (i.e.</Paragraph>
    <Paragraph position="2"> morphological derivations and synonyms) of lexical expansions performs better for a single question, even if all the three search strategies definitely perform better with questions with a limited number of expansions (i.e. two or three). An evaluation that will take into considerations such variations is planned for the near future. A crucial related problem for the future is that of the automatic evaluation of the search strategies (see Breck et al., 2000), which will enormously speed up the design and evaluation cycle.</Paragraph>
    <Paragraph position="3"> The experiments reported in this paper are part of a feasibility study for the realisation of a Natural Language Based search engine on the Web. At the present state of development, some steps in the query expansion (i.e. multiword recognition and synset selection) have been done manually, while both the keyword composition and the actual search are automatic and very efficient. In order to completely automate the process, the main source of inefficiency is likely to be keywords disambiguation in WordNet. The idea is to use a  two stage disarnbiguation algorithm (Voorhees, 1998), based on topic information, which performs linearly with respect to the number of words to be disambiguated.</Paragraph>
  </Section>
class="xml-element"></Paper>