6.1.7 What the Application Programmer Does
By the time you get to the point of designing the user interface, you have probably designed the rest of the application and know what the application objects are. At this point, you need to do the following:
Decide what types of application objects will be presented to the user as output and accepted from the user as input.
For each type of application object that the user will see, assign a corresponding presentation type. In many cases, this means simply using a predefined presentation type. In other cases, you need to define a new presentation type yourself. Usually the presentation type is the same as the class of the application object.
Use the application-building tools to specify the windows, menus, commands, and other elements of the user interface. Most of these elements will use the presentation types of your objects.
Common Lisp Interface Manager 2.0 User's Guide - 20 Sep 2011