DOCUMENT RETRIEVAL SYSTEM USING ANALOG SIGNAL COMPARISIONS FOR RETRIEVEL CONDITIONS INCLUDING RELEVANT KEYWORDS

A document retrieval system retrieves a registered document from a document database responsive to a designated retrieval condition including one or a plurality of designated keywords. The document retrieval system includes a storage for storing keyword relationships which indicate relationship values of keywords and relations of the keywords and registered documents, an input part for designating a retrieval condition including one or plurality of designated keywords, where the retrieval condition determines a registered document which is to be retrieved from the storage, a selector for selecting a plurality of keyword relationships based on the retrieval condition and for converting the selected keyword relationships into analog signals, an analog operation circuit for calculating a relevance of document based on the analog signals, and a converter for converting the calculated relevance of document into a digital value.