Classes And Class Hierarchy

One strength of the Pega platform is the reuse of rules between case types and applications. System architects often reuse rules - from single data elements to entire processes - in applications. The reuse of rules improves application quality and reduces development time.

Within an application,Pega groups rules according to their capacity for reuse. Each grouping is a class. Each application consists of three types of classes.

1. Workclass

The workclass contains the rules that describe how to process a case or cases,such as processes,data elements,and user interfaces.

2. Integration class

The integration class contains the rules that describe how the application interacts with other systems,such as a customer database or a third-party web server.

3. Data class

The data class contains the rules that describe the data objects used in the application,such as a customer or collection of order items.

A class can also contain other classes. A class that contains another class is called a parent class,while a class that is contained by another class is called a child class. A child class can reuse,or inherit,any of the rules defined for its parent class.
The work class contains a child class for each case type in your application. Each child class contains all of the rules unique to a case type,such as an auto insurance claim. The data class contains a child class for each data object.

The classes that comprise an application are called a class hierarchy. The class hierarchy determines how system architects can reuse rules within the application. The class hierarchy consists of several groups of classes:

1. Classes that describe a specific case type,such as expense reports or auto insurance claims 
2. Classes that collect common rules and data elements. These classes allow the reuse of rules at the division and organization level,such as an approval process shared across the entire IT department.
3. Classes from other applications,such as industry-specific Pega applications. So you can create a generic application for policy administration to use as a base for customizing versions for different countries.
4. Base classes provided by the Pega platform. These classes contain rules that provide basic functionality for processing cases. For example,the Pega platform provides data elements that record who created a case and the time needed to complete an assignment.

Any rule available to an application through the class hierarchy is considered in scope. Rules that an application can not access through the class hierarchy are considered out of scope.