System for generating a search formula by accessing search terms on the basis of a training set of pertinent and non-pertinent objects

An apparatus for automatically generating a search formula uses pertinent data and non-pertinent data given by the user. Suitable search terms are selected from the pertinent data on the basis of the term appearance ratios only in the pertinent data and in the given data. The respective effectiveness values of the search terms are calculated by using the number of pieces of pertinent data containing the term and the number of pieces of given data containing the term. Among the sums of the effectiveness values of the search terms included in respective pieces of pertinent data, the smallest sum is decided to be the threshold of effectiveness. Finally, the search formula consisting of search terms combined is generated on the basis of the threshold of effectiveness and the respective effectiveness values of the search terms.