Sentence Generation by Semantic Concordance

22 1965 International Conference on Computational Linguistics SENTENCE GENERATION BY SEMANTIC CONCORDANCE Toshiyuki Sakai and Makoto Nagao Department of Electrical Engineering, Kyoto University Kyoto, Japan ~ ~ '~a~l :~..:, ~"<,P.>~ o-~ o 'l Sakai & Nagao I ABSTRACT Generation of English sentence is realized in the following three steps. First, the generation of kernel sentence by phrase structure rules; second, the application of transformational rules to the kernel sentence; and fina- lly the completion of a sentence by the morphophonemic modifications. At the first stage of generating kernel sentence, the semantics of words are fully utilized. The method is such that a pair of words in the generat- ion process (subject noun and predicate verb, verb and object or complement, sdJective and modified noun etc.) is selected in accordance with the seman- tic categories which are attached to each word in the word dictionary. The semantic categories are determined by considering both the meaning of words themselves and also the functioning of words in sentences. At the stage of transformational rules, sentence is considered not as a simple string but as the one having the internal tree structure, and the transformational rules are applied to this tree structure. For these two stages the generation process is formalized strictly and is realized in a computer programming. We have presented in relation to the transformational rules a method of sentence generation not from the axiom (from th@ top Gf the tree) but from any point, from which the whole tree is constructed. We have also proposed that the morphophonemic rules can be presented as a kind of operators operating on words in the neighbourhood of a generated string. I. INTRODUCTION At present on behalf of the experience obtained from the research alre- ady done, we have fairly exact knowledge about the real difficulties in the MT research which are to be solved in the near future. Among these problems the most important ones might be how to construct the syntax of a language and how to grasp the semantics of sentences of the language. There have been many excellent contributions to the problems of syntax, but there are still few to the problems of semantics and the interrelation- ship between syntax and semantics. We have tried an investigation in this area by the method of generation of English sentence. The first paper ever published concerning the generation of sentences might have been that by Prof. V.H. Yngve of MIT in 1961. We have adopted the method once again from the following points of view. (i) it acts as a powerful test to the study of sentence structure, (ii) " to the study of semantics, (iii) " to the study of the relationship between syntax and semantics in natural language. Generally speaking the sentence generation method, contrary to the analysis of a given sentence (which is guaranteed to be a correct one), tends to demand the severe construction of syntactic rules and word selec- tion rules. It may seem at the present level …

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