Multilingual machine translation: A case study of Spanish-English reflexives.

摘要

This dissertation describes a formalism for multilingual machine translation and its application to the translation of reflexive constructions between Spanish and English. The language description is principle-based, with linguistic rules divided between language-specific components and shared language-independent components. The principles define head projection and the licensing of attachments to the projection. Rules create linguistic objects as tree structures, where nodes are represented as feature structures (attribute-value pairs). Feature unification, augmented with negative, disjunctive, and conditional constraints, defines the feature content of the objects. Translation is accomplished by defining levels of representation based on morphological, syntactic, and semantic (predicate-argument) structures, and by defining structural transformations between levels. Language transfer is based on the Principle of Semantic Compatibility, in which semantic representations (trees and features) across languages are unifiable with each other. Using this formalism, rule components for English and Spanish are defined which maximize rule-sharing; only ten phrase structure rules are required for a substantial subset of the English and Spanish languages. All grammatical relations are expressed in terms of local trees (root node and immediate daughters). Arguments and modifiers are licensed in canonical position, and displaced arguments may appear either in subject or clitic position. A displaced argument is associated with its predicate not by movement but by unifying features within a chain structure spanning all of the local trees between the argument and the predicate. Given this linguistic model, an implementation of reflexives is described in which a reflexive pronoun discharges either an internal or an external argument. If an internal argument is discharged, a personal reflexive construction results, as in Juan se vio 'Juan saw himself'. If an external argument is discharged, a nonpersonal reflexive construction results, as in Se venden periodicos 'Newspapers are sold'. In both personal and nonpersonal reflexive constructions, the sentential subject, whether lexical or null, binds the reflexive. In the nonpersonal reflexive construction, a pleonastic null subject binds the reflexive. A Reflexive Principle, implemented over local trees, determines when a pronoun is reflexive and when not, depending on the binding potential of an undischarged external argument.