How is the abstract class in a UML model expressed in the geodatabase?

Note:
This article pertains to ArcGIS versions 9.x only. Later versions of ArcGIS may contain different functionality, as well as different names and locations for menus, commands and geoprocessing tools.

An abstract class in a UML model does not have a direct representation in the geodatabase. It is a modeling artifact, used to model fields that are common to many tables or feature classes in a single place. When the model is used to create a geodatabase, the fields in primary or abstract classes are made part of the derived tables or feature classes.