<?xml version="1.0" standalone="yes"?>
<Paper uid="P98-1109">
  <Title>Know When to Hold 'Em: Shuffling Deterministically in a Parser for Nonconcatenative Grammars*</Title>
  <Section position="2" start_page="0" end_page="663" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> Although there has been a considerable amount of research on parsing for constraint-based grammars in the HPSG (Head-driven Phrase Structure Grammar) framework, most computational implementations embody the limiting assumption that the constituents of phrases are combined only by concatenation. The few parsing algorithms that have been proposed to handle more flexible linearization constraints have not yet been applied to nontrivial grammars using nonconcatenative constraints. For example, van Noord (1991; 1994) suggests that the head-corner parsing strategy should be particularly well-suited for parsing with grammars that admit discontinuous constituency, illustrated with what he calls a &amp;quot;tiny&amp;quot; fragment of Dutch, but his more recent development of the head-corner parser (van Noord, 1997) only documents its use with purely concatenative grammars. The conventional wisdom has been that the large search space resulting from the use of such constraints (e.g., the shuffle relation) makes parsing too inefficient for most practical applications. On the other hand, grammatical analyses of languages that have more flexible ordering of constituents than English make frequent use of constraints of this type. For example, in recent work by Dowty (1996), Reape (1996), and Kathol &amp;quot; This research was sponsored in part by National Science Foundation grant SBR-9410532, and in part by a seed grant from the Ohio State University Office of Research; the opinions expressed here are solely those of the authors.</Paragraph>
    <Paragraph position="1"> (1995), in which linear order constraints are taken to apply to domains distinct from the local trees formed by syntactic combination, the nonconcatenative shuffle relation is the basic operation by which these word order domains are formed. Reape and Kathol apply this approach to various flexible word-order constructions in German.</Paragraph>
    <Paragraph position="2"> A small sampling of other nonconcatenative operations that have often been employed in linguistic descriptions includes Bach's (1979) wrapping operations, Pollard's (1984) head-wrapping operations, and Moortgat's (1996) extraction and infixation operations in (categorial) type-logical grammar.</Paragraph>
    <Paragraph position="3"> What is common to the proposals of Dowty, Reape, and Kathol, and to the particular analysis implemented here, is the characterization of natural language syntax in terms of two interrelated but in principle distinct sets of constraints: (a) constraints on an unordered hierarchical structure, projected from (grammatical-relational or semantic) valence properties of lexical items; and (b) constraints on the linear order in which elements appear. In this type of framework, constraints on linear order may place conditions on the the relative order of constituents that are not siblings in the hierarchical structure. To this end, we follow Reape and Kathol and utilize order domains, which are associated with each node of the hierarchical structure, and serve as the domain of application for linearization constraints. null In this paper, we show how it is possible to avoid searching the large space of permutations that results from a nondeterministic application of shuffle constraints. By delaying the application of shuffle constraints until the linear position of each element is known, and by using an efficient encoding of the portions of the input covered by each element of an order domain, shuffle constraints can be applied deterministically. The results of our implementation demonstrate that this optimization of shuffle constraints yields a dramatic improvement in the overall performance of a head-corner parser for German.</Paragraph>
    <Paragraph position="4"> The remainder of the paper is organized as follows: SS2 introduces the nonconcatenative fragment  (1) Seiner Freundin liess er ihn helfen his(DAT) friend(FEM) allows he(NOM) him(ACC) help 'He allows him to help his friend.' (2) Hilft sie ihr schnell help she(NOM) her(DAT) quickly 'Does she help her quickly?' (3) Der Vater denkt dass sie ihr seinen Sohn helfen liess</Paragraph>
    <Paragraph position="6"> of German which forms the basis of our study; SS3 describes the head-corner parsing algorithm that we use in our implementation; SS4 discusses details of the implementation, and the optimization of the shuffle constraint is explained in SS5; SS6 compares the performance of the optimized and non-optimized parsers.</Paragraph>
  </Section>
class="xml-element"></Paper>