Some Problems of Prepositional Phrases in Machine Translation

Abstract

Prepositions as functional words play an important role in the construction of phrases and sentences. They connect typically a noun or a pronoun to another word and show their relationships in a sentence. They are a kind of “small” word and can not stand alone in the sentences. However, they often pose great problems in the identification of their relationships to other constituents. Prepositional phrase (PP) attachment is especially problematic in machine translation. Besides, as prepositions by themselves are semantically very ambiguous, the translation of these words poses challenge to machine translation (MT) too. This paper discusses how some of the PP attachments and other problems concerned with PPs are resolved in an experimental English-Chinese MT system by applying controlled language technique that we have developed in the context of safety-critical applications. Examples are extracted from a small parallel bilingual corpus focused on medical protocols in English and Chinese, where the usages, in particular some of the syntactic structures, vary a lot in many aspects. It is suggested that such ambiguities can be resolved by means of lexical information, such as subcategorizations, selection constraints and other additional information.