What is Abstract class and Concrete class :
Abstract class: – An abstract class is a rule (an instance of Obj-Class Rule-class) created to support the definition of the rules, including other classes. These rules can be inherited by the subclasses of the abstract class. The rules with a class as a key component (such as properties, activities, flows, models, etc.) can apply to an abstract class.
Concrete class: – A concrete class can have instances stored in the database. However, an abstract class cannot have any instances. A selection of the class form determines whether a class is abstract or concrete. On the Class Browser screen, shape identifies a concrete class.For all but a few classes, a dash or minus sign (-) character as the last character in the class name indicates that the class is abstract and may contain ‘ other (abstract or concrete) classes. For example, the class and the class Rule- Work-Cover- are abstract classes, while labor and overall coverage is a concrete class. concrete classes usually appear near or at the bottom (leaf nodes) of the class hierarchy, but can occur anywhere below the top.