The Class is an instance of rule ‘Rule-Obj-Class’.
The class can be created as ‘Abstract Class’, ’Concrete Class’, or ‘Class Group’.
Class Group is a concrete class while creating it is mentioned as ‘is a Class Group. The basic purpose of creating a Class Group is to group the classes; we are making a set of classes that share a common key structure. All instances of these classes to be stored in a single database table.