Data processing system

A method and system provides a prototypical object 220 which can be copied to create a derived object. A derived object can contain attribute values or it can hold a reference to its prototypical object. If a required value is not held by the prototypical object, the object searches up an object hierarchy to find the required attribute. In addition, each object can register an interest in a prototypical object that contains required attributes. If an attribute of a prototypical object changes, the prototypical object informs all registered objects of the change. At runtime, the prototypical object becomes a master object whose attribute values can be changed by the user, whereby changes in master object attributes are propagated to all registered derived objects.