2. A knowledge base system for retrieving information by using a concept relation model which expresses knowledge y a plurality of interconnected nodes, each node represents a concept corresponding to information included in said node, said node being connected to other nodes by links, each of said links represents a relation between concepts represented by nodes connected by said link, comprising: a first memory for storing concept names corresponding to said nodes, each concept name corresponds to a concept; a second memory for storing information representing subsumption relations between different concepts corresponding to links connected between said concepts; a third memory for storing information representing definitions of different kinds of relations; a fourth memory for storing information representing relations between different concepts corresponding to links connected between said concepts; and relation deducting means for inputting concept names from a user of said system and deducting relations between concepts indicated by said inputted concept names by using knowledge stored in said first to fourth memory; retrieval means for retrieving information from at least one of said nodes based on said inputted concept names and said relations deducted by said relation deducting means; a fifth memory for storing syntax rules for understanding at least one natural language; a sixth memory for storing a lexicon, which can be edited based on the content of said first and third memories; lexical analysis means for effecting lexical analysis by inputting a sentence written in the natural language and referring to information coming from said sixth memory; syntactic analysis means for forming possible sentence structures based on results of the lexical analysis and information stored in said fifth memory; and means for extracting and selecting only sentence structures appropriate in meaning relative to the inputted sentence formed based on a result of syntactic analysis by said relation deducting means.
2. A knowledge base system for retrieving information by using a concept relation model which expresses knowledge y a plurality of interconnected nodes, each node represents a concept corresponding to information included in said node, said node being connected to other nodes by links, each of said links represents a relation between concepts represented by nodes connected by said link, comprising: a first memory for storing concept names corresponding to said nodes, each concept name corresponds to a concept; a second memory for storing information representing subsumption relations between different concepts corresponding to links connected between said concepts; a third memory for storing information representing definitions of different kinds of relations; a fourth memory for storing information representing relations between different concepts corresponding to links connected between said concepts; and relation deducting means for inputting concept names from a user of said system and deducting relations between concepts indicated by said inputted concept names by using knowledge stored in said first to fourth memory; retrieval means for retrieving information from at least one of said nodes based on said inputted concept names and said relations deducted by said relation deducting means; a fifth memory for storing syntax rules for understanding at least one natural language; a sixth memory for storing a lexicon, which can be edited based on the content of said first and third memories; lexical analysis means for effecting lexical analysis by inputting a sentence written in the natural language and referring to information coming from said sixth memory; syntactic analysis means for forming possible sentence structures based on results of the lexical analysis and information stored in said fifth memory; and means for extracting and selecting only sentence structures appropriate in meaning relative to the inputted sentence formed based on a result of syntactic analysis by said relation deducting means. 4. A knowledge base system according to claim 2, wherein said syntactic analysis means outputs all the sentence structures, which are possible in view of the syntax rules as results of the syntactic analysis and deducts appropriateness in the meaning based on an assembly of facts stored in a knowledge base described by the concepts and the relations to select and output only those which are appropriate in the meaning, among the results of said syntactic analysis.