The EER approach by itself is insufficient to complete the design of an object-oriented database. The EER approach must be supported with a technique that identifies and documents the behavior of each class of object. This involves a detailed analysis of the processing requirements of the enterprise. In a conventional data flow approach using Data Flow Diagrams (DFDs), for example, the processing requirements of the system are analyzed separately from the data model. In object-oriented analysis, the processing re- quirements are mapped on to a set of methods that are unique for each class. The methods that are visible to the user or to other objects (public methods) must be distinguished from methods that are purely internal to a class (private methods). We can identify three types of public and private method: