PLATON--A New Programming Language for Natural Language Analysis

American Journal of Computational Linguistics Microfiche 37 28 MAKOTO NAGAO AND JUN-ICHI TSUJII Department of Electrical Engineering Kyoto University Kyoto, Japan ABSTRACT PLATON (Programming LAnguage for Tree OperatioN) facilities of pattern matching and flexible backtracking, language is developed t~ simplify writing analysis programs The pattern matching process has the facility to extract sub- input sentence and invoke semantic and contextual checking fo?. actions between syntactic and other components are easily obt processing results i n a failure, a message which expresses t : failure will be sent up. The control w i l l be modified accoru enables us to write f a i r l y complicated non-deterministic progr manner. An example of structural analysis using PLATON is als - ,le 1. The 1 language Erom thc Intc - -. rf Ise of . Th i :- ;in:; e d " I Introduction In t h i s paper we describe a new programming language which is designed to facilitate the writing of natural language grammars. A simple structural analysis program using this language is given as an example. There are two key issues in analyzing natural language by computer: 1) how to represent knowledge (semantics, pragmatics) and the state (context) of the world, and 2) how to advance the programming technology appropriate for syntactic- semantic, syntactic-contextual interface. The point in designing a programming language is to make this kind of programming less painful. T r a d i t i m a 1 systems whi.ch represent grammars as a set of rewriting rules ustially 'have poor control mechanisms, and flexible interaction between thc syntact LC and other con~ponents is not possible. Systems in which rules o f gr-;lnmlilrs .rlrc cn11,i-dilcd i n proccdrlrcs, an. tllc other hand, make it p o s s i b l c to i n t t - r m i s ttrct 6 yrltnc t 'lc and seniant i c anaIyst?s i n an i r~tiinnte way. Llowcvcr, thest. systcos are apt. t.0 c.lestroy the intc.lligih:il ity and regularity of natural language gramars, because i n these systems both rules and their control mechanisms are contained i n the same program. Recently various syscems for natural language analysis have been developed T. Winograd's (1971) "PROGRAMMAR" i s a typical example of procedure oriented systems. In this system the syntactic and other components can interact closely i n the course of analyzing sentences. However, d e t a i l s of the program are lost i n the richness of this interaction. LINGOL, developed by V . Pratt (1973) at MIT, is a language appropriate to syntax- semantics interface and in which it is easy t o write grammars in the form of rewriting rules. The TAUM group a t Montreal University (1971) has evolved a programming languagc name :I System-Q in which expressions of trees, strings and lists of them can be matched against p a r t i a l expressions ( s t r u c t u r …

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