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<Paper uid="P93-1019">
  <Title>FEATURE-BASED ALLOMORPHY* Hans-Ulrich Krieger Hannes Pirker</Title>
  <Section position="7" start_page="144" end_page="145" type="concl">
    <SectionTitle>
4 Conclusions
</SectionTitle>
    <Paragraph position="0"> In this section we examine our proposal vis-b.-vis others, suggest future directions, and provide a summary.</Paragraph>
    <Section position="1" start_page="144" end_page="145" type="sub_section">
      <SectionTitle>
4.1 Comparison to other Work
</SectionTitle>
      <Paragraph position="0"> Computational morphology is a large and active field, as recent textbooks (Sproat 1992 and Ritchieet al. 1992) testify* This impedes the identification of particularly important predecessors, among whom nonetheless three stand out. First, Trost 1991's use of two-level morphology in combination verbal rule inherited from the more general adjectival rule, but pursuing this here would take us somewhat afield.</Paragraph>
      <Paragraph position="1">  with feature-based filters was an important impetus. Second, researchers at Edinburgh (Calder 1988, Bird 1992) first suggested using FDLs in phonological and morphological description, and Bird 1992 suggests describing FA in FDL (without showing how they might be so characterized, however--in particular, providing no FDL definition of what it means for an FA to accept a string).</Paragraph>
      <Paragraph position="2"> Third, Cahill 1990 posed the critical question, viz., how is one to link the work in lexical inheritance (on morphotactics) with that in finite-state morphology (on allomorphy). This earlier work retained a separation of formalisms for allomorphy (MOLUSC) and morphotactics (DATR). Cahill 1993 goes on to experiment with assuming all of the allomorphic specification into the lexicon, in just the spirit proposed here. 11 Our work differs from this later work (i) in that we use FDL while she uses DATR, which are similar but not identical (cf. Nerbonne 1992); and (ii) in that we have been concerned with showing how the standard model of allomorphy (FA) may be assumed into the inheritance hierarchy of the lexicon, while Cahill has introduced syllable-based models.</Paragraph>
    </Section>
    <Section position="2" start_page="145" end_page="145" type="sub_section">
      <SectionTitle>
4.2 Future Work
</SectionTitle>
      <Paragraph position="0"> At present only the minimal examples in Section 2 above have actually been implemented, and we are interested in attempting more. Second, a compilation into genuine finite state models could be useful. Third, we are concerned that, in restricting ourselves thus far to acceptors over two-level alphabets, we may incur parsing problems, which a more direct approach through finite-state transducers can avoid (Sproat 1992, p.143). See Ritchie et al. 1992, 19-33 for an approach to parsing using finite-state acceptors, however.</Paragraph>
    </Section>
    <Section position="3" start_page="145" end_page="145" type="sub_section">
      <SectionTitle>
4.3 Summary
</SectionTitle>
      <Paragraph position="0"> This paper proposes a treatment of allomorphy formulated and processable in typed feature logic. There are several reasons for developing this approach to morphology. First, we prefer the GENERALITY of a system in which linguistic knowledge of all sorts may be expressed--at least as long as we do not sacrifice processing efficiency. This is an overarching goal of HPSG (Pollard and Sag 1987)--in which syntax and semantics is described in a feature formalism, and in which strides toward descriptions of morphotactics (Krieger 1993a, Riehemann 1993, lICf. Reinhard and Gibbon 1991 for another sort of DATR-based allomorphy Gerdemann 1993) and phonology (Bird 1992) have been taken. This work is the first to show how allomorphy may be described here. The proposal here would allow one to describe segments using features, as well, but we have not explored this opportunity for reasons of space.</Paragraph>
      <Paragraph position="1"> Second, the uniform formalism allows the exact and more transparent specification of dependencies which span modules of otherwise different formalisms. Obviously interesting cases for the extension of feature-based descriptions to other areas are those involving stress and intonation--where phonological properties can determine the meaning (via focus) and even syntactic well-formedness (e.g., of deviant word orders). Similarly, allomorphic variants covary in the style register they belong to: the German dative singular in -e, dera Kinde, belongs to a formal register.</Paragraph>
      <Paragraph position="2"> Third, and more specifically, the feature-based treatment of allomorphy overcomes the bifurcation of morphology into lexical aspects-which have mostly been treated in lexical inheritance schemes--and phonological aspects-which are normally treated in finite-state morphology. This division has long been recognized as problematic. One symptom of the problem is seen in the treatment of nonphonologically conditioned allomorphy, such as German umlaut, which (Trost 1990) correctly criticizes as ad hoc in finite-state morphology because the latter deals only in phonological (or graphemic) categories. We illustrated the benefits of the uniform formalism above where we showed how a similar nonphonologically motivated alternation (German schwa epenthesis) is treated in a feature-based description, which may deal in several levels of linguistic description simultaneously. null</Paragraph>
    </Section>
  </Section>
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