Unit-to-Unit Interaction as a Basis for Semantic Interpretation of Japanese Sentences

UNIT-TO-UNIT INTERACTION AS A BASIS FOR SEMANTIC INTERPRETATION OF JAPANESE SENTENCES Hozumi TANAKA ELECTROTECHNICAL LABORATORY, 1-1-4 UMEZONO, SAKURA-MURA, NIIHARI-GUN, IBARAKI-KEN, JAPAN ABSTRACT: The notion of UNIT-to-UNIT inter- action is introduced to analyse dependency relations between words in a sentence. A UNIT is a basic framework for concept representation and is composed of many slots. After generating a parsed tree from an input sentence, our se- mantic interpretation begins traversing.the tree from right to left to discern the case frame in a stage as early as possible, since Japanese is a language in which verb is in the sentence- final and has a case frame. UNIT-to-UNIT inter- action, which is performed at each node of the parsed tree, follows a bottom-up progression. There are UNIT descriptions at terminal (bottom) nodes and the UNIT descriptions are modified or merged into other UNITs in the course of the interaction. The results of the interaction will be transferred to upper nodes. The inter- action process continues on upward until the top node; at this point, the semantic structure of the input sentence is finally obtained. The notion of UNIT-to-UNIT interaction is feasibly applicable to semantic interpretation of English. i. INTRODUCTION Semantic processing is very important for us to build a natural language (NL) under- standing system. It will be true that semantics takes precedence over syntax when human beings understand language. Based on this assumption, some NL understanding system designers have totally abandoned the traditional use of grammars for linguistic analysis. They are based on special procedures of semantic inter- pretation to build up semantic structures, and the result of syntactic parsing is not used. Such systems without grammar often lack formalism. We should not totally abandon a traditional use of grammars for linguistic analysis, since results of syntactic parsing fill the gap be- tween an input sentence and its semantic structure. We have developed Extended LINGOL [13,12] that is the extended version of Pratt's LINGOL [8,9]. Pratt's LINGOL has a very good formalism to merge syntactic and semantic information. The idea is that the result of syntactic parsing, a parsed tree, is considered as a program tree which is evaluated at the time of semantic interpretation. In the course of the interpretation, UNIT-to-UNIT interactions are performed. Thus a parsed tree of LINGOL corresponds to an analysis tree of Montague grammar and the evaluation phase of the parsed tree is analogous to the translation phase of Montague grammar [3] (See the See.6). Our Extended LINGOL inherits the semantic interpretation method from the original Pratt's LINGOL. After generating a parsed tree from an input sentence, semantic interpretation is set out. The parsed tree is composed of context- free rules to each of which a LISP program is attached. In other words, at each node of the tree, there is a program for making semantic interpretation. As will be explained in the Sec. 5.,UNIT-to-UNIT interaction will take place at each node of the program tree. The interaction process continues on upward until the top node, at …

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