1. A method of obtaining a value via a rule engine implemented by a collection object in an object-oriented application, said method comprising: receiving a request for a value from an object-oriented application, said request including a key and being directed to a method of a collection object associated with said object-oriented application, wherein said collection object is capable of storing said key, storing data associated with said key, and providing said data in response to said receiving said request; responsive to said receiving, processing said request by a rule engine external to said object-oriented application, said processing replacing said providing said data by said collection object via said method of said collection object being overridden to invoke said rule engine; identifying, via said processing said request, a rule included in a rule definition file external to said application, said identifying based on said rule being associated with said key included in said request, said rule definition file including an algorithm associated with said rule; and executing said algorithm via said processing said request, said executing providing said value.