Consider how you might use the list and group mechanisms with transactions related to a company's salary operations.
Assume that some transactions used by the salary administrators are used every day. For example, a transaction for handling an employee's tax details may have to be performed at any time. Other transactions, such as minor weekly or monthly payroll adjustments, are run at predefined intervals, or on specific days or dates. You would therefore not want to include the same mixture of transactions and programs every time the system was started up.
By creating a resource definition group for taxation transactions, and another for payroll transactions, you could add them to different lists to produce the required system tables for different days. In the above example, one list would identify only the taxation group; the other would identify both taxation and payroll groups. You would specify the appropriate list in a system initialization parameter.
Clearly, a real system would have many more groups and lists than this.