Abstract: A method for programming a computer, and software products for implementing the method, are disclosed. According to the method, objects are created which, upon execution of the system, may initiate actions and may acquire values. A specification of relevance criteria is stored as an attribute of each object. Relevance criteria, which may refer to the values of other objects, describe all conditions necessary and sufficient to make the binary decision for whether the object will be considered relevant to the program's operation during execution. Action criteria may also be specified to control the actions of a relevant object. The method is particularly well suited for programming expert systems, but may be used for programming any type of computer program.