From the IBM Manual "Systems Application Architecture: Common User Access Basic Interface Design Guide" (SC26-4583):
" Although the text subset of the graphical model is generally preferred for all new applications on the non-programmable terminal, there are some applications whose structure and objectives may warrant an exception to that rule. They are:
An application with only limited actions that can be performed on the primary object or objects in the application. This is true of many data-entry-intensive applications where the only application action available is 'Enter data'. This type of application does not need an action bar because only a limited number of actions are available to users. Either the actions or the objects in this type of application may be implicit, or the actions and objects are combined. These limited-action applications typically are designed to maximize the resources of a host system by minimizing the required number of host interrupts.
A new version of an existing action-object-oriented application does not involve a major re-design of the application. One of the prime objectives for this style of application might be to retain consistency with previous versions for users who will be upgrading to a new version. However, components being used in the application, such as 'entry fields' and 'selection fields', should be revised to conform to CUA. These applications also might have been designed to minimize the number of host interrupts generated by the application.
An application that should be an action-object, as determined by a thorough task analysis. This decision may have been made because the intended users have a current conceptual model of the application that is action-object.
An application that is designed to be 'walk-up-and-use' by users who are constantly new, and, therefore, will not be trained. Such applications must control the users' choices very closely. An example is an information display in a hotel or airport lobby. These applications typically combine object and action choices. They might be object-action or action-object, but they would not include an action bar and, therefore, would be entry model applications. "