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Báo cáo khoa học: "JPSG Parser on Constraint Logic Programming"

Prolog is frequently used in implementing natural language parsers or generators based on unification based grammars. This is because Prolog is also based on unification, and therefore has a declarative feature. One important characteristic of unification cu-Prolog adopts constraint unification instead of based grammar is also a declarative grammar formalthe normal Prolog unification. In cu-Prolog, con- ization [11]. However, Prolog does not have sufficient power of straints in terms of user defined predicates can be expressing constraints because it executes every parts directly added to the program clauses. . | JPSG Parser on Constraint Logic Programming TUDA Hirosi Department of information science Faculty of science University of Tokyo 7-3-1 Kongo Bunkyo-ku Tokyo 113 Japan e-mail a30728 tansei.cc.u-tokyo.junet@relay.cs.net HASIDA Kôiti Institute for New Generation Computer Technology ICOT 1-4-28 Mita Minato-ku Tokyo 108 Japan e-mail hasida@icot.jp@relay.cs.net SIRAI Hidetosi Tamagawa University 6-1-1 Tamagawa gakuen Machida-shi Tokyo 194 Japan e-mail a88868 tansei.cc.u-tokyo.junet@relay.cs.net Abstract This paper presents a constraint logic programming language cu-Prolog and introduces a simple Japanese parser based on Japanese Phrase Structure Grammar JPSG as a suitable application of cu-Prolog. cu-Prolog adopts constraint unification instead of the normal Prolog unification. In cu-Prolog constraints in terms of user defined predicates can be directly added to the program clauses. Such a clause is called Constraint Added Horn Clause CAHC . Unlike conventional CLP systems cu-Prolog deals with constraints about symbolic or combinatorial objects. For natural language processing such constraints are more important than those on numerical or boolean objects. In comparison with normal Prolog cu-Prolog has more descriptive power and is more declarative. It enables a natural implementation of JPSG and other unification based grammar formalisms. From this April Fujitsu Corporation 1 Introduction Prolog is frequently used in implementing natural language parsers or generators based on unification based grammars. This is because Prolog is also based on unification and therefore has a declarative feature. One important characteristic of unification based grammar is also a declarative grammar formalization 11 . However Prolog does not have sufficient power of expressing constraints because it executes every parts of its programs as procedures and because every variable of Prolog can be instantiated with any objects. Hence the constraints in unification based grammar are forced to .