13. The program product according to claim 12 , wherein said calculating operation comprises causing the computer to calculate said exclusion efficiency, for an individual common keyword of said plurality of common keywords stored in said storage means except for said selected keyword, based on a first parameter indicating a level of exclusion efficiency in a set of data that is associated with said selected keyword when said keyword is specified as the exclusion keyword and a second parameter indicating a level of exclusion efficiency in a set of all of said searching object data when said keyword is specified as the exclusion keyword.
13. The program product according to claim 12 , wherein said calculating operation comprises causing the computer to calculate said exclusion efficiency, for an individual common keyword of said plurality of common keywords stored in said storage means except for said selected keyword, based on a first parameter indicating a level of exclusion efficiency in a set of data that is associated with said selected keyword when said keyword is specified as the exclusion keyword and a second parameter indicating a level of exclusion efficiency in a set of all of said searching object data when said keyword is specified as the exclusion keyword. 15. The program product according to claim 13 , further comprising an operation for causing the computer to automatically set the contribution levels of said first parameter and said second parameter to said exclusion efficiency in accordance with the kind of said searching object data.