1. A data retrieving computer apparatus for retrieving data satisfying a user request from data stored in a computer file, comprising: a term defining means having quantitatively defined therein fuzzy terms assigned to each item to be retrieved in a form of rate ranges, a previously set retrieving condition range for each of said terms and a distribution curve having a function associated therewith and representing a satisfaction data distribution within said retrieving condition range for each of said terms; a condition analyzing means responsive to an input fuzzy term of an item to be retrieved for analyzing an input retrieving condition equation including said input fuzzy term and converting said input retrieving condition equation into a value-based retrieving condition equation using information from said term defining means, said input fuzzy term included in said input retrieving condition equation being changed to numerical values in said value-based retrieving condition equation; a data retrieving means for retrieving data from said computer file in accordance with said value-based retrieving condition equation supplied from said condition analyzing means: a satisfaction degree evaluating means coupled to said data retrieving means, for calculating a satisfaction degree for each retrieved data from said data retrieving means using a corresponding said distribution curve, and for outputting a calculated said satisfaction degree; and a data narrowing means for narrowing said retrieved data from said data retrieving means to obtain narrowed data representing a sub-set of said retrieved data, said data narrowing means performing said narrowing using a same said value-based retrieving condition equation upon said retrieved data.