Element Classes
Elements are objects contained within an object. The element classes listed in an object class definition indicate what kinds of elements objects of that object class can contain. An object can contain many elements or none, and the number of elements of a particular class that it contains may change over time. Most application and system objects can contain elements.The definition in Figure 5-1 shows that a paragraph object can include word elements. It is possible for a paragraph to have no words. At a later time, the same paragraph might have many words.