"g. , controller updates user's shopping cart) A view uses the model to generate an appropriate user interface (e . g. , view produces a screen listing the shopping cart contents). The view gets its own data from the model (or direct from the data access layer - sometimes there is no domain logic to do). 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. Allied Model Trains 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. "

" 219 - 222. [2] Wieringa, R. J. ; "Algebraic foundations for dynamic conceptual models"; PhD dissertation Free University of Amsterdam; 17 May 1990. [3] Kaschek, R. ; "Modeling ontology use for information systems"; In: Althoff, K. -D. Broadway Limited Model Trains & Dengel, A. & Bergmann, R. "