An apparatus for storage, selective inspection, and execution of complex, contingent rules, comprises a computer having one or more central processing units, a user interface, and magnetic, optical, or other media for data and program storage and retrieval. Rules are defined partly as programs and partly as data. Access procedures for selecting certain appropriate rules under the defined conditions. A display or other output procedures for conveying the results of the rule selections to people, to the computer executing the rules, and to other computers.