This section describes the two main Entity classes (Entity and ManagedEntity).<br/>This is an abstract class that extends the RootEntity class in order to represent classes of objects that play a business function and that may be managed. The top-level Entity class hierarchy is shown in following Figure below.<br/>ManagedEntity further defines Entity by providing the two attributes and the associations ManagedEntity has with other entities. This allows an instance of any entity that inherits from Entity to be defined as a being managed by creating an instance of an association to an instance of ManagedEntity.<br/>ManagedEntity does not itself inherit from RootEntity for the following reasons:<br/><ul>
<li>If it inherits from RootEntity then it further defines Entity by duplicating the three attributes that are already in Entity (that it inherits from RootEntity).</li></ul>
<ul>
<li>The composition association between Entity and ManagedEntity with its 0,1 multiplicity is what is often called an “IsA” association, which is much like sub-classing.  So if ManagedEntity inherits from RootEntity then it is inheriting attributes it already “inherits” from Entity via the “IsA”.</li></ul>
ManagedEntity is further described in the next section.<br/>