Restriction and Correspondence-based Translation

Restriction and Correspondence-based Translation Ronald M. Kaplan Xerox Palo Alto Research Center 3333 Coyote Hill Road Palo Alto, California 94304 USA Kaplan.Parc@Xerox.Com Jiirgen Wedekind Institute for Natural Language Processing University of Stuttgart Azenbergstr. 12 D-7000 Stuttgart 1, FRG Juergen@ims.uni-stuttgart.de Abstract Kaplan et al. (1989) present a framework for translation based on the description and correspondence concepts of Lexical- Functional Grammar (Kaplan and Bresnan, 1982). Certain phenomena, in particular the head-switching of adverbs and verbs, seem to be problematic for that approach. In this paper we suggest that these difficulties are more properly considered as the result of defective monolingual analyses. We propose a new description-language operator, restriction, to permit a succinct formal encoding of the informal intuition that semantic units sometimes correspond to subsets of functional information. This operator, in conjunction with an additional recursion provided by a description-by-analysis rule, is the basis of a more adequate account of head-switching that preserves the advantages of correspondence-based translation. 1. Introduction Kaplan et al. (1989) present a framework for translation based on the description and correspondence concepts of Lexical-Functional Grammar (Kaplan and Bresnan, 1982). LFG formulates the syntactic dependencies and generalizations of natural languages in terms of the properties of formal structures of different types: ordinary phrase-structure trees represent the surface constituency of sentences while hierarchical finite functions represent their underlying grammatical relations. The structures for a particular sentence are those that satisfy descriptions produced from annotated phrase-structure rules and lexical entries. The description of the more abstract functional structure is determined by the dominance and precedence relations of the superficial constituent structure, given the assumption that there is a piecewise correspondence function that maps the nodes in the c-structure tree into the units of the f-structure. Kaplan (1987) and Halvorsen and Kaplan (1988) extend this structure/description/correspondence architec- ture to provide modular and declarative characterizations of the relationships between syntactic structures and other levels of linguistic representation. Kaplan et al. (1989) suggest that this architecture can provide a formal basis for specifying complex source-target translation relationships in a declarative fashion that builds on monolingual grammars and lexicons that are independently motivated and theoretically justified. In particular, the approach permits features from different linguistic levels to affect translation without requiring that reflexes of those disparate features appear together in an otherwise unmotivated transfer or interlingual representation. Kaplan et al. (1989) offer several examples to illustrate the effectiveness of this approach to translation. These examples involve changes in grammatical functions from source to target, differences in control, and differences in embedding (or head-switching). The Kaplan et al. solutions depend on monolingual representations of phrasal, functional, and semantic information related by the correspondences ~p and a, with translation 193 correspondences • and ~' mapping source to target structures, as shown in the configuration in (1): (1) Source " " Target • ' semantic structure O --------.-~ O °/ ~' ~° f_structur e o ~_..__.._..-------~ o di) 0 / ~ ~: c-structure These solutions utilize the formal device of codescription to specify the target structure constraints …

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