Dealing With Conjunctions in a Machine Translation Environment

DEALING WITH CONJUNCTIONS IN A MACHINE TRANSLATION ENVIRONMENT Xiumlng HUANG Institute of Linguistics Chinese Academy of Social Sciences BeiJing, China* ABSTRACT The paper presents an algorithm, written in PROLOG, for processing English sentences which contain either Gapping, Right Node Raising (RNR) or Reduced Conjunction (RC). The DCG (Definite Clause Grammar) formalism (Pereira & Warren 80) is adopted. The algorithm is highly efficient and capable of processing a full range of coordinate constructions containing any number of coordinate conjunctions ('and', 'or', and 'but'). The algorithm is part of an English-Chinese machine translation system which is in the course of construction. 0 INTRODUCTION Theoretical linguists have made a considerable investigation into coordinate constructions (Ross 67a, Hankamer 73, Schachter 77, Sag 77, Gazdar 81 and Sobin 82, to name a few), giving descriptions of the phenomena from various perspectives. Some of the descriptions are stimulating or convincing. Computational linguists, on the other hand, have achieved less than their theoretical counterparts. (Woods 73)'s SYSCONJ, to my knowledge, is the first and the most often referenced facility designed specifically for coordinate construction processing. It can get the correct analysis for RC sentences like (i) John drove his car through and completely demolished a plate glass window but only after trying and failing an indefinite number of times, due to its highly non- deterministic nature. (Church 79) claims '~ome impressive initial progress" processing conjunctions with his NL parser YAP. Using a Marcus-type attention shift mechanism, YAP can parse many conjunction constructions including some cases of Gapping. It doesn't offer a complete solution to conjunction processing though: the Gapping sentences YAP deals with are only those wlth two NP remnants in a Gapped conjunct. * Mailing address: Cognitive Studies Centre, University of Essex, Colchester C04 3SQ, England. (McCord 80) proposes a "more straightforward and more controllable" way of parsing sentences like (I) within a Slot Grammar framework. He treats "drove his car through and completely demolished" as a conjoined VP, which doesn't seem quite valid. (Boguraev 83) suggests that when "and" is encountered, a new ATN arc be dynamlcally constructed which seeks to recognise a right hand constituent categorlally similar to the left hand one just completed or being currently processed. The problem is that the left-hand conjunct may not be the current or most recent constituent hut the constituent of which that former one is a part. (Berwlck 83) parses successfully Gapped sentences like (2) Max gave Sally a nickel yesterday, and a dime today using an extended Marcus-type deterministic parser. It is not clear, though, how his parser would treat RC sentences llke (I) where the fi~t conjunct is not a complete clause. The present work attacks the coordinate construction problem along the lines of DCG. Its coverage is wider than the existing systems: both Gapping, RNR and RC, as well as ordinary cases of coordinate sentences, are taken into consideration. The work is a major development of (Huang 83)'s CASSEX package, which in turn was based on (Boguraev 79)'s work, a system for resolving …

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