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<Paper uid="W04-2006">
  <Title>A step towards incremental generation of logical forms</Title>
  <Section position="3" start_page="0" end_page="0" type="intro">
    <SectionTitle>
2 Motivation
</SectionTitle>
    <Paragraph position="0"> In 1992, an exhaustive study of the Portuguese tourist resources was made by the Direc,c~ao Geral de Turismo (DGT) and afterwards the Inventory of Tourist Resources (IRT) emerged.</Paragraph>
    <Paragraph position="1"> In order to access it, multimedia &amp;quot;kiosks&amp;quot; were developed and a system called Edite (da Silva, 1997; Reis et al., 1997; da Silva et al., 1997) was created with the purpose of being integrated in these &amp;quot;kiosks&amp;quot; and to allow database access using natural language. Edite had a set of linguistically motivated traditional modules (semantic rules associated with syntactic rules, bottom-up parser, and so on) and it soon became saturated: adding a new syntactic rule caused dramatic side effects, a new semantic value could duplicate the number of generated formulas, etc. It was this experiment that made us change our approach and invest in a more robust methodology. We found in the 5P Paradigm (B`es, 1999; B`es and Hag`ege, 2001; Hag`ege, 2000) the background we were looking for and the syntax-semantic interface presented in this paper reflects the effort of adapting to a more robust methodology.</Paragraph>
    <Paragraph position="2"> Many systems base their interface in rules, that according to (A&amp;quot;it-Mokhtar et al., 2002) &amp;quot;encode hypothetical local interpretations of sub-strings, yet to be validated by the production of a full parse&amp;quot;. This is typically what happens to syntactic-semantic bottom-up parsers where each semantic rule is associated with a syntactic rule. Even if these systems do not fail when a sub-string interpretation fails, their parsers need to deal with a combinatory explosion of multiple interpretations of words, even if syntactic conditions would allow precise values to be chosen. This is due to the fact that at each step there is not a whole vision of the (syntactic) context. An additional effect of not having access to context is that spurious ambiguities are produced.</Paragraph>
    <Paragraph position="3"> As an example, consider the Portuguese word qualquer (roughly, any), which can take several semantic values (see (M'oia, 1992) for a detailed discussion about the multiple interpretations of  qualquer): * In Qualquer c~ao gosta de ossos (All dogs like bones) it has an universal value (univ); * In Ele tem qualquer problema (There is some problem with him) it has an existential value (exist); * In Ele 'e um jornalista qualquer (He is an insignificant journalist) it is an adjective, and it means something like with no relevant characteristics in the class denoted by the noun it qualifies. We will denote this semantic value as indiscriminate; * In Ele n~ao 'e um jornalista qualquer (He is  not an insignificant journalist) it has the same indiscriminate value.</Paragraph>
    <Paragraph position="4"> Let us assume that on the right of a main verb in the scope of negation, qualquer can only take the indiscriminate semantic value. Typically, in a bottom-up parsing (Figure 3) we will not be able to discard unnecessary values, as in point (1), when finally we have the whole vision of the subtree, the semantic rule will not take into consideration the negation inside V.</Paragraph>
    <Paragraph position="5">  Another kind of interface can be found in systems such as ExtrAns (Moll'a et al., 2003), where the syntax-semantic interface is executed over dependencies. According to (Moll'a and Hutchinson, 2002), the current version of ExtrAns uses either Link Grammar or the Conexor FDG parser.</Paragraph>
    <Paragraph position="6"> In the first situation, the logical-form is constructed by a top-down procedure, starting in the head of the main dependency and following dependencies. The algorithm is prepared to deal with a certain type of dependencies, and whenever an unexpected link appears, a special recovery treatment is applied. When describing the algorithm, the authors say that most of these steps &amp;quot;... become very complex, sometimes involving recursive applications of the algorithm&amp;quot; and also that &amp;quot;specific particularities of the dependency structures returned by Link Grammar add complexity to this process&amp;quot; (Moll'a and Hutchinson, 2002).</Paragraph>
    <Paragraph position="7"> In the Conexor FDG case, the bottom up parser used has three stages. In the first one (introspection) possible underspecified predicates are associated with each word. Object predicates introduce their own arguments, but other predicates remain incomplete until the second stage (extrospection). During extrospection, arguments are filled by examing the relation between each word and its head. Sometimes dummy arguments need to be assigned when the algorithm faces disconnected dependency structures. A third stage (re-interpretation) is needed to re-analyse some logical constructs.</Paragraph>
    <Paragraph position="8"> According to the authors, the algorithm cannot produce the correct argument structure for long distance dependencies.</Paragraph>
    <Paragraph position="9"> As we will see, within AsdeCopas: * rules allow to identify semantic values that depend on the context; * the algorithm itself is independent from the utilised dependency structures. Only semantic rules have to be adapted to the dependency structures; * there is no need to recursively apply the algorithm or to create dummy arguments due to disconnected dependency structures: in these situations, default rules are triggered; * long distance dependencies cause no problem as rules are sensitive for the (possibly non-local) syntactic context; * all words, independently from their category, are mapped into formulas in one step: since rules are self-contained, they contain all the necessary information to calculate the corresponding formula.</Paragraph>
  </Section>
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