For relatively simple applications where a data object is retrieved, manipulated and saved again, the foregoing definition of an application object will suffice. However, the situation often arises when an application must perform some processing that is rather more complicated. Either the application must interface with another system or external device or a certain work task must be performed in a particular sequence of operations that is critical to the correct completion of the task. The incorporation of such requirements into the object-oriented paradigm requires an expansion of the application object concept.
The key to successful expansion of the object-oriented paradigm lies in the definition of a data object. Whereas a data object was previously defined as a manifestation of a logical data entity, the definition will now be expanded to include any other type of logical entity or source of information, such as an external system or a procedures manual.