In the very beginning of this book we said something along these lines: would it not be nice if...
You would have an extensive library of UI widgets that could be used in the same way as HTML?
You could extend HTML with new widgets and components in any way you like?
You could use AJAX almost transparently?
You could bind data retrieved from the server in flexible ways to any widget, in particular data grids?
We explained in this book that the Backbase framework allows you to develop applications answering these questions with a resounding "yes". A square web application is a single page application that uses BTL, TDL, XHTML, CSS, and data-bound widgets, and nothing else.
That may sound obvious at first, but it actually isn't. You can use the Backbase framework in any way you wish, also for traditional multi-page applications, with just a few BTL widgets, or with JavaScript all across the page. The framework may be slow if you try to do so because of the overhead...