" It is worth noting that the concept of solution to a problem depends on the investigator, its purpose, intended means of investigation, time-horizon of that investigation and so forth. What has been presented here so far essentially is due to Stachowiak, [1] . To understand how then models are used in more detail one needs to distinguish from each other the various reference modes in which the investigator puts the model with respect to the original. The reference modes that perhaps are most important in computing are: (1) descriptive, i. e. , the model describes the original. If the deviation from model to original cannot be tolerated then the model has to be changed. Large Scale Model Airplane Analysis models are in a descriptive reference mode to their originals. (2) prescriptive, i. "

" The model should have no direct knowledge of the view. However, the observer pattern can be used to provide some indirection between model and view, allowing the model to notify interested parties of a change. A view object can register itself with the model and listen for changes but the model itself remains view-agnostic. The controller does not pass domain objects (the model) to the view although it might issue a command telling the view to update itself. The user interface waits for further user interactions, which begins the cycle anew. Benefits and liabilities Although widely used, MVC has both advantages and disadvantages compared to other design options, and individual circumstances should be used to choose the most appropriate design. We discuss some of those here. Rubber Powered Model Airplane View instability vs. model stability If constructed correctly, models can enjoy a fair degree of stability (owing to the stability of the domain model), whereas user interface code usually undergoes frequent and sometimes dramatic change (typically because of usability problems, the need to support growing classes of users, or simply the need to keep the application looking "fresh"). "