Identify the abstract classes in the XML schema and mark them in the UML class diagram. Diagrams written with such an intent can be easily translated. What are the restrictions that a UML class diagram must satisfy so that it is easily translated into an XML schema. This rule disallows classes that can have only circular objects. Classes are partitioned into abstract classes and concrete classes.
Abstract classes have at least one subclass.
That means that all superclasses should be abstract. The parts of each class need to be ordered. There is policy for adding the parts of a superclass in a systematic way to the parts of the subclasses. Replace undirected associations by two directed associations. Follow the ordering of parts and the ordering policy.