The deeper your understanding of your application, the more confidently you can abstract from its lower-level details to a “bigger picture” view, one that organizes related programs in functional, structural, or other types of groupings: a Customer Maintenance subsystem, for example, in an Order Acceptance application. This is the kind of view a subject matter expert uses to evaluate whether an application does everything it is supposed to do, in the appropriate order.
The Diagrammer black-box feature lets you assign lower-level objects to higher-level groupings that make it easy to visualize their roles in your application. Your diagram might have one black box for the Customer Maintenance subsystem, another for the Order Entry subsystem, and so forth. Because the details of these relationships are hidden in the black box until you need to view them, the subject matter expert can home in quickly on the higher-order functions you have abstracted from them.
You use the Tag Manager to identify the items in each higher-level grouping. Each grouping can, in turn, reference a more inclusive grouping. If you assign the Customer Maintenance tag to one set of programs, for example, and the Order Entry tag to another, and both tags reference the Application Functions tag, then when you choose Application Functions in the Diagrammer Group By drop-down, the Diagrammer puts the programs in black boxes named Application Functions Customer Maintenance and Application Functions Order Entry.