Dealing With Conjunctions in a Machine Translation Environment

DEALING WITH CONJUNCTIONS IN A MACHINE TRANSLATION ENVIRONMENT Xiuming Huang Institute of Linguistics chinese Academy of Social Sciences Beijing, China* ABSTRACT A set of rules, named CSDC (Conjunct Scope Determination Constraints), is suggested for attacking the conjunct scope problem, the major issue in the automatic processing of conjunctions which has been raising great difficulty for natu- ral language processing systems. Grammars embody- ing the CSDC are incorporated into an existing A~{ parser, and are tested successfully against a wide group of "and" conjunctive sentences, which are of three types, namely clausal coordination, phrasal coordination, and gapping. With phrasal coordina- tion the structure with two NPs coordinated by "and" has been given most attention. It is hoped that an ATN parser capable of dealing with a large variety of conjunctions in an efficient way will finally emerge from the present work. 0 INTRODUCTION One of the most complicated phenomena in English is conjunction constructions. Even quite simple noun phrases like (i) Cats with whiskers and tails are structurally ambiguous and would cause problem when translated from English to, sa~-, Chinese. Since in Chinese all the modifiers of the noun should go before it, two different translations in Chinese might be got from the above phrase: (la) (With whiskers and tails) de (cats) ("de" is a particle which connects the modifiers and the modifieds); (ib) ((With whiskers) de (cats)) and (tails). Needless to say, a machine translation system should be able to analyse correctly among ether things the conjunction constructions before high quality translation can be achieved. As is well known, ATN (Augmented Transition Network) grammars are powerful in natural language * Mailing address: Cognitive Studies Centre University of Essex Colchester COb 3SQ, England. parsing and have been widely applied in various NL processing systems. However, the standard ATN grsamars are rather weak in dealing with con- junctions. In (Woods 73), a special facility SYSCONJ for processing conjunctions was designed and imple- mented in the LUNAR speech question-answering sys- tem. It is capable of analysing reduced conjunc- tions impressively (eg, "John drove his car through and completely demolished a plate glass window"), but it has two drawbacks: first, for the processing of general types of conjunction con- structions, it is too costly and too inefficient; secondly, the method itself is highly non-deter- ministic and easily results in combinatorial ex- plosions. In (Blackwell 81), a WRD AND arc was propos- ed. The arc would take the interpreter from the final to the initial state of a computation, then analyse the second argument of a coordinated con- struction on a second pass through the ATN net- work. With this method she can deal with some rather complicated conjunction constructions, but in fact a WRD AND arc could have been added to nearly every state of the network, thus making the grammar extremely bulky. Furthermore, her syste~ lacks the power for resolving the ambiguities con- tained in structures like (1). In the machine translation system designed by (Nagao et al 82), when dealing with conjunctions, …

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