The XML Form Object Model consists of models that each contain a set of objects. Each object is derived from one of the set of classes that define common properties and methods. An object, in turn, inherits these common properties and methods but may also add properties and methods that are unique to that object, relative to other objects derived from the same class.
As with traditional class structures, each class inherits properties and methods from its parent class. Objects, in turn, inherit from the parent class from which they derive.
Each model uses a hierarchy of objects. Objects do not inherit properties and methods from other objects, but instead inherit directly from the class hierarchy. The hierarchy of objects within a model represents the XML structure of that model.

XML Form Object Model Class Hierarchy