From the IBM Manual "Systems Application Architecture: Common User Access Basic Interface Design Guide" (SC26-4583):
" For an application with numerous available actions and/or an application whose users need to understand the objects and their relationships, the object-action orientation is recommended. Some of the major reasons for this recommendation are:
The object-action orientation avoids what are often referred to as 'action modes', which force users to switch from one mode to another to perform different actions on the same object.
In a large system or an application with many actions, the action-object approach may require clustering of actions into higher levels, or categories, of action types, This often results in very large, complicated menu hierarchies. With the object-action approach, only the actions applicable to the users' chosen objects are presented. This avoids the need for large menu hierarchies.
The object-action orientation combined with the visual approach used in CUA supports user exploration and user control, because only the actions applicable to selected objects are available to users. Users can view all available actions and perform them in the desired order, rather than in an order dictated by the application.
In the action-object orientation, actions that apply to multiple objects may have to be given slightly different names, for example, synonym verbs, to distinguish their uses. Users may be confused by the similar action names or be led to believe that more actions are available for a given object than there actually are. With the object-action orientation, the same action name can be used for all objects to which it applies. The application knows how to tailor the action to the chosen object; users, therefore, do not have to distinguish among synonyms.
The larger the number of possible actions, the more difficult it is to refine and nest action types and names consistently and unambiguously. The general categories into which finer distinctions and actions are grouped may not be very meaningful in themselves. They often exist only for the purpose of grouping and may be arbitrary, abstract, or redundant. The object-action orientation, as noted previously, allows the application to offer only the actions applicable to the users' chosen objects. Hierarchies of action types and actions can therefore be minimized."
