A Statistical Approach to Language Translation

A STATISTICAL APPROACH TO LANGUAGE TRANSLATION P. BROWN, J. COCKE, S. DELI,A PIETRA, V. DELLA PIETRA, F. JELINEK, R, MF, RCF, R, and P. ROOSSIN IBM Research Division T.J. Watson Research Center Department of Computer Science P.O. Box 218 Yorktown Heights, N.Y. 10598 ABSTRACT An approach to automatic translation is outlined that utilizes technklues of statistical inl'ormatiml extraction from large data bases. The method is based on the availability of pairs of large corresponding texts that are translations of each other. In our case, the iexts are in English and French. Fundamental to the technique is a complex glossary of correspondence of fixed locutions. The steps of the proposed translation process are: (1) Partition the source text into a set of fixed locutioris. (2) Use the glossary plus coutextual information to select tim corresponding set of fixed Ioctttions into a sequen{e forming the target sentence. (3) Arrange the words of the talget fixed locutions into a sequence forming the target sentence. We have developed stalistical techniques facilitating both tile autonlatic creation of the glossary, and the performance of tile three translation steps, all on the basis of an aliglnncllt of corresponding sentences in tile two texts. While wc are not yet able to provide examples of French / English tcanslation, we present some encouraging intermediate results concerning glossary creation and the arrangement of target WOl'd seq lie)lees. 1. INTRODUCTION In this paper we will outline an approach to automatic translation that utilizes techniques of statistical information extraction from large data bases. These self-organizing techniques have proven successful in the field of automatic speech recognition [1,2,3]. Statistical approaches have also been used recently in lexicography [41 and natural language processing [3,5,6]. The idea of automatic translation by statistical (information thco,'etic) methods was proposed many years ago by Warren Weaver [711. As will be seen in the body of tile paper, tile suggested technique is based on the availability of pairs of large corresponding texts that are Iranslations of each other. Ill particular, we have chosen to work with the English and French languages because we were able to obtain the biqingual llansard corpus of proceedings of the Canadian parliament containing 30 million words of text [8]. We also prefer to apply our ideas initially to two languages whose word orcter is similar, a condition that French and English satisfy. Our approach eschews the use of an internmdiate ,nechalfism (language) that would encode the "meaning" of tile source text. The proposal will seem especially radical since very little will be sakl about employment of conventional grammars. This omissiol], however, is not essential, and may only rcl'lect our relative lack of tools as well as our uncertainty about tile degree of grammar sophistication required. We are keeping an open mind! Ill what follows we will not be able to give actual results el French / English translation: our less than a year old project is not I'ar enongh ahmg. Rather, we will outline our current thinking, sketch certain techniqttes, and substantiate our Ol)timism …

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