System for processing natural language including identifying grammatical rule and semantic concept of an undefined word

• US 5,109,509 A
• Filed: 11/28/1988
• Issued: 04/28/1992
• Est. Priority Date: 10/29/1984
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yoshiura, Horishi, Nakanishi, Kunio, Katayama, Yasunori, Hirasawa, Kotaro
• Primary Examiner(s): Lee, Thomas C.
• Assistant Examiner(s): Mohamed, Ayni
• Application Number:
  US07/277,526
• Time in Patent Office: 1,247 Days
• Field of Search: 364/200 MS File, 364/900 MS File, 364/419
• US Class Current: 704/9
• CPC Class Codes: G06F 40/211 Syntactic parsing, e.g. based on context-free grammar [CFG] or unification grammars
• CPC Class Codes: G06F 40/242 Dictionaries
• CPC Class Codes: G06F 40/268 Morphological analysis
• CPC Class Codes: G06F 40/30 Semantic analysis
• CPC Class Codes: G06F 40/47 Machine-assisted translation, e.g. using translation memory

Abstract

A natural language including Japanese, Korean, Chinese, etc., is suitably processed when an undefined word which is not registered in a dictionary appears in an input character train. When the undefined word appears, a semantic analysis processor decides a semantic concept of the undefined word by using a case dictionary. Further, by using a vocabulary hierarchy dictionary, which registers vocabularies in a hierarchy structure, the semantic analysis processor extracts a group of vocabularies (synonyms) corresponding to a lower concept of the semantic concept of the undefined word. The natural language processing can be achieved practically and efficiently with dictionaries of a limited storage capacity.

Claims

1. A natural language processing apparatus for processing a natural language character train, said processing apparatus comprising:

a keyword dictionary for storing keywords;

a conjunction relation dictionary for storing conjunction relationships of keywords stored in said keyword dictionary;

morphemic analysis means including (a) means for receiving an inputted character train including defined words and undefined words;

(b) means for comparing the character train with keywords in said keyword dictionary to identify an undefined word in the character train;

(c) means for comparing the character train with the contents of said conjunction relation dictionary to determine the conjunction relationship of the identified undefined word; and

(d) means for dividing the inputted character train into vocabularies;

a grammatical rule dictionary for storing grammatical rules related to the natural language;

syntax analysis means for determining whether a conjunction of the vocabularies is in conformity with a predetermined grammatical rule stored in said grammatical rule dictionary;

a case dictionary for storing semantic concepts corresponding with the natural language, including superior concepts and subordinate concepts, the semantic concepts being in conformity with the predetermined grammatical rule;

semantic analysis means responsive to the semantic concepts stored in said case dictionary for identifying a semantic concept of the identified undefined word, said semantic analysis means including (a) a vocabulary hierarchy dictionary for storing vocabularies classified in a hierarchal order from a superior concept to a subordinate concept in accordance with a semantic concept of the vocabularies stored in said case dictionary, and (b) means for extracting from said hierarchy dictionary a group of vocabularies corresponding to a subordinate concept of the semantic concept of the undefined word; and

a display device for displaying the extracted group of vocabularies to permit selection by an operator of a synonym of the undefined word.

2. A natural language processing apparatus for processing a natural language character train, said processing apparatus comprising:

a keyword dictionary for storing keywords;

a conjunction relation dictionary for storing conjunction relationships of keywords stored in said keyword dictionary;

morphemic analysis means including (a) means for receiving an inputted character train including defined words and undefined words;

(b) means for comparing the character train with keywords in said keyword dictionary to identify an undefined word in the character train;

(c) means for comparing the character train with the contents of said conjunction relation dictionary to determine the conjunction relationship of the identified undefined word; and

(d) means for dividing the inputted character train into vocabularies;

a grammatical rule dictionary for storing grammatical rules related to the natural language;

syntax analysis means for determining whether a conjunction of the vocabularies is in conformity with a predetermined grammatical rule stored in said grammatical rule dictionary;

a case dictionary for storing semantic concepts corresponding with the natural language, including superior concepts and subordinate concepts, the semantic concepts being in conformity with the predetermined grammatical rule;

semantic analysis means responsive to the semantic concepts stored in said case dictionary for identifying a semantic concept in the outlet of said syntax analysis means, including a semantic concept of the identified undefined word, said semantic analysis means including (a) a vocabulary hierarchy dictionary for storing vocabularies classified in a hierarchal order from a superior concept to a subordinate concept in accordance with a semantic concept of the vocabularies stored in said case dictionary, and (b) means for extracting from said hierarchy dictionary a group of vocabularies corresponding to a subordinate concept of the semantic concept of the undefined word; and

inference means for selecting from the extracted group of vocabularies a synonym to replace the undefined word in conformity with the inputted character train.

3. A method for processing a natural language by extracting an undefined word from an input character train, comprising the steps of:

receiving an input character train including an undefined word;

dividing the received input character train into vocabularies;

determining whether a conjunction of the vocabularies is in conformity with a predetermined grammatical rule;

identifying a semantic concept of the undefined word by using a case dictionary which stored semantic concepts between vocabularies, the stored semantic concepts including superior concepts and subordinate concepts and being in conformity with the predetermined grammatical rule;

extracting from a vocabulary hierarchy dictionary, which stores vocabularies in a hierarchal order from a superior concept to a subordinate concept, a group of vocabularies corresponding to a subordinate concept of the identified semantic concept of the undefined word; and

selecting from the extracted group of vocabularies a synonym for the undefined word.

4. A method of processing a natural language character train, including an undefined word, said method comprising the steps of:

receiving an input character train having a conjunctional relationship and including defined words and undefined words;

dividing the received character train into words;

identifying a grammatical rule with which the conjunctional relationship of the received character train is in conformity;

applying the identified grammatical rule to a case dictionary storing semantic concepts to identify a semantic concept of the undefined word;

extracting from a vocabulary hierarchal dictionary a vocabulary of words corresponding to a subordinate concept of the identified semantic concept; and

selecting synonyms of the undefined word from the extracted vocabulary.