Blurred understanding: MVC is recursive, not flat (Score 5, Informative)

I don't understand this concept of MVC "blurring".

For every instance of MVC, the View component itself can be a complete, nested MVC unit or even a collection of MVC units. This is the nature of the MVC design pattern.

For example, take the humble HTML button. It is its own complete MVC machine. It has a Model (button state, color, size, etc) and controller logic that responds to events (render "down" state, "focus" state, etc.). And of course it has a graphical View.

This MVC button machine can delegate events and control to a parent MVC machine, such as an HTML table.

Delegation continues to parent MVCs at ever higher abstraction layers until finally we're at the level of browser-as-complete MVC machine. The next higher layer involves the server back end, and now the browser is the view component of the server/browser abstraction layer.

If the server implements its GUI interface layer as servlets, for example, then the servlet/browser is a complete MVC machine. But this layer still does not contain the core business logic, since for any well-designed (non-trival) server it should be possible to completely replace the GUI layer (such as Struts, etc) with another GUI framework without affecting the core business logic/data. And so the browser/servlet layer becomes the view component of the highest MVC layer, which has the core business logic as the model and controller.

The MVC pattern supports a recursive tree of MVC state machines, typically managed as parent-child relationships. Low level business logic, such as preventing alpha characters from being entered into a SSN text input field, can be implemented directly in the input field widget's MVC machine. High level business logic/data, such as validating and submitting a complex shopping order, takes place on the highest level MVC state machine.

Business logic/data, like any complex computer science problem, can consist of many different levels of abstraction. It is absurd to think that the business logic of a non-trivial business application can be neatly separated into just three components of a single MVC state machine existing at a single level of abstraction. And so I just don't get this idea of blurring, unless it is just one person's understanding of hierarchal abstraction layers that is blurred, which has nothing to do with a limitation of MVC.

The challenge is in how to create code on the browser that fully leverages the MVC pattern. If code is to be as well organized, refactorable, and maintainable on the browser side as it is on the server side, an MVC machine needs the full OOP paradigm for expression. That's why tools such as GWT have become so attractive. Tools as these make it practical and affordable to distribute all business logic, high and low, to the proper layer of abstraction -- be it at the widget level, tile level, page level, server level, system level, or enterprise level.