8. A non-transitory computer readable recording medium storing a program to cause a computer to execute the processing including: (a) reading a database to generate a free itemset that includes a set of items of attribute-value pairs in the database, and that has a frequency in the database greater than or equal to a predetermined threshold value set in advance, and storing the generated free itemset in a storage unit; (b) generating a rule candidate that includes a condition part having the generated free itemset set thereto and a consequent part having an item that does not share an attribute with the free itemset set thereto and that has a confidence greater than or equal to a confidence threshold value set in advance, and storing the generated rule candidate in a storage unit, when a ratio of a frequency of the itemset obtained by adding one item x to a free itemset α to a frequency of the free itemset α is greater than or equal to the confidence threshold value, adding to a list of a rule candidate group including a plurality of the rule candidates a rule including a condition part having a free itemset α set thereto and a consequent part having the one item x set thereto; and (c) checking minimality of each of the generated rule candidates and outputting the rule candidate to an output apparatus when the rule candidate is determined to be minimal.
8. A non-transitory computer readable recording medium storing a program to cause a computer to execute the processing including: (a) reading a database to generate a free itemset that includes a set of items of attribute-value pairs in the database, and that has a frequency in the database greater than or equal to a predetermined threshold value set in advance, and storing the generated free itemset in a storage unit; (b) generating a rule candidate that includes a condition part having the generated free itemset set thereto and a consequent part having an item that does not share an attribute with the free itemset set thereto and that has a confidence greater than or equal to a confidence threshold value set in advance, and storing the generated rule candidate in a storage unit, when a ratio of a frequency of the itemset obtained by adding one item x to a free itemset α to a frequency of the free itemset α is greater than or equal to the confidence threshold value, adding to a list of a rule candidate group including a plurality of the rule candidates a rule including a condition part having a free itemset α set thereto and a consequent part having the one item x set thereto; and (c) checking minimality of each of the generated rule candidates and outputting the rule candidate to an output apparatus when the rule candidate is determined to be minimal. 9. The non-transitory computer readable recording medium storing a program according to claim 8 , wherein when the rule candidate is determined to be minimal in the processing (c), the process of outputting the rule candidate to the output apparatus includes: sorting the list of the rule candidate group including the generated rule candidates in an ascending order of sizes of the rule candidates; sequentially extracting a minimal one or more of the rule candidates from a head of the list and outputting the extracted minimal one or more of the rule candidates to the output apparatus; and removing, from the list, one or more of the remaining rule candidates in the list that are redundant with respect to the output minimal one or more of the rule candidates.