Abstract: A means is provided for specifying, applying, and managing sets of temporary or permanent additions or modifications to the behavior of object-oriented programs without having to change the code of the program, by using externalized rules. The points at which the externalized rules may be applied is determined by the implementation object model, thus making their specification natural to the program developers who are familiar with the program's implementation object model. The concept of dynamic method-based trigger or control points is disclosed for identifying potential rule attachment points in objects and identifying the rules that are applicable to each dynamic control point.