INFORMATION RETRIEVAL SYSTEM WITH MEANS FOR ANALYZING UNDEFINED WORDS IN A NATURAL LANGUAGE INQUIRY

An information retrieval system is adapted to carry out information retrieval by entering an inquiry sentence in natural language, executing semantic analysis of the natural language inquiry sentence by a semantic analysis unit, and producing a retrieval condition from a result of the semantic analysis. The information retrieval system is provided in its semantic analysis unit with an undefined word processing unit which classifies an undefined word in the inquiry sentence in accordance with a process of producing a retrieval condition from the semantic analysis of other words contained in the inquiry sentence, the undefined word being defined as a word unregistered in a dictionary provided therein and incapable of direct semantic analysis, and displays a result of processing for the undefined word classified. The undefined word processing permits operation of information retrieval to be done without discontinuation.