I spoke to Jeff Lejeune, RIM’s Advanced User Interface Director, here at BlackBerry DevCon Europe in Amsterdam.

He is part of the team responsible for the Cascades UI, a native code UI framework for the forthcoming BlackBerry 10 OS. One of the things he told me is that the Cascades name is actually being used for parts of the API beyond the user interface. It is a major part of the new operating system.

I had not appreciated until today the extent of the likely difference between BlackBerry 10 and the current Tablet OS 1.0 or Playbook OS 2.0. Since the PlayBook OS is already based on QNX, I had assumed that BlackBerry 10 would be an incremental update rather than a radical new direction.

Certainly there is less difference between PlayBook OS 2.0 and BlackBerry 10 then there is between BlackBerry 7.0 and the PlayBook OS, so my assumption was not completely wrong. That said, the introduction of the Cascades UI acquired with The Astonishing Tribe is a major change. Lejune told me that Cascades UI will be in effect the native UI of BlackBerry 10, and the built-in apps will use it.

The first version of the PlayBook uses both native code and Adobe AIR for its built-in apps.

RIM has given full backing to Adobe AIR at this event, presenting it as one of the supported development platforms and saying that it will support AIR for as long as Adobe does and maybe even longer. Even so, it would be fair to say that RIM is moving away from AIR and towards native code and Cascades UI in BlackBerry 10.

Further, Adobe itself has changed direction since the launch of the PlayBook last year. Adobe has made it clear that while Flash, Flex and AIR are still important, its strategic direction is HTML 5 when it comes to development platforms. Some aspects of Flex, the code-based approach to AIR authoring, are being wound down, including the visual designer in Flash Builder.

My sense therefore is that AIR is not the best choice if you are considering how to develop for BlackBerry 10 – and BlackBerry 10 is the future of RIM’s platform. The primary choice should be between Cascades UI, for best performance and integration, or WebWorks (PhoneGap), for development in HTML and JavaScript and cross-platform code.