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Classes and class hierarchy


Pega Platform™ facilitates rule reuse between case types and applications. Developers often reuse rules, from single data elements to entire processes, in applications. Rule reuse improves application quality and reduces development time. Within an application, Pega Platform groups rules into classes according to their capacity for reuse. Each grouping is a class. Each application consists of three class types:

  • The Work class contains the rules that describe how to process cases, such as processes, data elements, and user interfaces.
  • The Integration class contains the rules that describe how the application interacts with other systems, such as the integration assets that connect the application to an external customer database or a third-party web server.
  • The Data class contains the rules that describe the data types in the application, such as a customer data type or an order items data type.
Note: When you create a rule in App Studio, the application identifies the appropriate class for you. 

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Parent and child classes

A class can also contain other classes. A class that contains another class is a parent class, while a class that is contained by another class is a child class. A child class can reuse or inherit any of the rules that are defined for its parent class.

In the following image, click the + icons to learn more about the parent and child classes.

Note: In Dev Studio > App Explorer, you can view the classes and their relationships in your application. To learn more about class hierarchy and inheritance, see Understanding class hierarchy and inheritance.

Class hierarchy

Classes are layered into a multi-level class hierarchy to organize application assets. Classes are organized from most-specific to least-specific in the class hierarchy. The class hierarchy determines how developers can reuse rules within the application. The application can use any rule that is available to an application through the class hierarchy. The application cannot use rules that an application cannot access through the class hierarchy. 

When attempting to identify the rule to use at run time, Pega Platform starts with the most-specific class and expands the search to more general classes.

The name of each class identifies the position of the class within the class hierarchy. Consider the TGB-IT-Work class. A hyphen separates each level of the class hierarchy (-), which means that TGB-IT-Work is a child of the TGB-IT class, which is a child of the TGB class.

In the following image, click the + icons to learn more about the groups of classes in the class hierarchy.

Note: To support the organization's need for rule reuse, the Lead System Architect (LSA) and Project leaders typically design the class hierarchy before building the application.

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