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<Paper uid="P98-1056">
  <Title>Syntactic and Semantic Transfer with F-Structures*</Title>
  <Section position="2" start_page="0" end_page="341" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> Target and source levels of representation in transfer-based machine translation (MT) are subject to often competing demands: on the one hand, they need to abstract away from particulars of language specific surface realization to ensure that transfer is as simple and straightforward as possible. On the other hand, they need to encode sufficiently fine-grained information to steer transfer. Furthermore, target and source representations should be linguistically well established and motivated levels of representation. Finally, from a computational perspective they need to be sensible representations for both parsing and generation. LFG f-structures are abstract, &amp;quot;high-level&amp;quot; syntactic representations which go some way towards meeting these often irreconcilable requirements.</Paragraph>
    <Paragraph position="1"> &amp;quot; We would like to thank H. Kamp, M. Schiehlen and the anonymous reviewers for helpful comments on earlier versions of this article. Part of this work was funded by the German Federal Ministry of Education, Science, Research and Technology (BMBF) in the framework of the Verbmobil project under grant 01 IV 701 N3.</Paragraph>
    <Paragraph position="2"> Correspondence-based transfer on f-structures has been proposed in (Kaplan et al., 1989).</Paragraph>
    <Paragraph position="3"> A closer look at translation problems involving structural mismatches between languages in particular head switching phenomena (Sadler and Thompson, 1991) - led to the contention that transfer is facilitated at the level of semantic representation, where structural differences between languages are often neutralized. Structural misalignment is treated in semantics construction involving a restriction operator (Kaplan and Wedekind, 1993) where f-structures are related to (possibly sets of) disambiguated semantic representations.</Paragraph>
    <Paragraph position="4"> Given the high potential of semantic ambiguities, the advantage of defining transfer on semantic representations could well be counter-balanced by the overhead generated by multiple disambiguated structures as input to transfer. This and the observation that many semantic (and syntactic) ambiguities can be preserved when translating into a target language that is ambiguous in similar ways, sheds light on the issue of the properties of representations for the task of defining transfer.</Paragraph>
    <Paragraph position="5"> In principle, the problem of semantic ambiguity in transfer can be tackled in a number of ways. Packed ambiguity representation techniques (Maxwell III and Kaplan, 1993) could be integrated with the approach in (Kaplan and Wedekind, 1993). In the linear logic based semantics of (Dalrymple et al., 1996) scope ambiguities are accounted for in terms of alternative derivations of meaning assignments from a set of meaning constructors. Ambiguity preserving semantic transfer can be devised on sets of meaning constructors rather than disambiguated meanings (Genabith et al., 1998).</Paragraph>
    <Paragraph position="6"> Transfer on packed representations is considered  in (Emele and Dorna, 1998).</Paragraph>
    <Paragraph position="7"> In the present paper we consider alternative approaches to transfer on underspecified - syntactic or semantic - representations, focusing on issues of modularity, reusability and practicality, interfacing existing implemented approaches in a flexible way. At the same time, the proposals readdress the issue of what is an appropriate level of representation for translation, in view of the known problems engendered by structural mismatches and semantic ambiguity.</Paragraph>
    <Paragraph position="8"> We first show how the underlying machinery of the semantic-based transfer approach developed in Dorna and Emele (1996b) can be ported to syntactic f-structure representations.</Paragraph>
    <Paragraph position="9"> Second, we show how the underspecified semantic interpretation approach developed in Genabith and Crouch (1997) can be exploited to interface f-structure representations directly with the named semantic-based transfer approach.</Paragraph>
    <Paragraph position="10"> Third, we compare the two approaches with each other, and with co-description and restriction operator based approaches.</Paragraph>
  </Section>
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