A method and apparatus for providing dynamic classification of objects. The system provides for dynamic classification of objects within a simulator environment and also contains a graphical user interface related to the simulator environment. The apparatus includes a display, a processor, and an input device. A processor generates a simulation environment on a display screen and a user interfaces to the system with a user input device. Objects within a simulation take on user specified rules and properties that define their behavior. A graphical representation is provided for categorizing classes of objects. A graphical representation of a jar provides a label for defining the identity of the jar and a first region into which items (e.g., icons representing instances or classes of objects) can be dragged and dropped. These items become members of the dynamic class defined by the jar. A second region of the jar defines items that are specifically excluded from the set of items defined by the contents of the first region. Items can be dragged and dropped into the second region. Since scope of the contents of a jar is wide, jars allow a user to define and redefine a class of unrelated objects without being confined to a hierarchical data structure. Behavior can be defined with respect to items categorized by a particular jar. Further, jar membership is inherited in that any instances having an ancestor class occurring in the jar belong to the jar themselves.