Abstract: A development tool for a network based data processing system comprises a document type developer for assembling document types from prestored object components and for associating a set of states with each document type. Each state defines at least one document property. The document types are used to instantiate documents to form a data processing system, and to provide the data processing system with state assignment functionality. The data processing system assigns each instantiation a succession of states, where each state is taken from the instantiation's set of states, thus applying the state's respective property to the instantiation. A succession of properties is thereby defined for the document type instantiation over the instantiation's life cycle.