I saw this video of Dennis Wixon talking about what NUI is, the core principals, and what might come after NUI and I had to repost it here. Video via Jonathan Brill.
Dennis Wixon | UX Week 2008 | Adaptive Path from Adaptive Path on Vimeo.
I've seen this basic material presented several times by different people, notably Micrsoft's August De Los Reyes, who has a very exciting presentation style. Dennis in this video also did a very good job presenting the material in an engaging way as well as tying the material into his personal credentials and back story.
When he started, he began doing the recent Microsoft presentation fad of introducing presentations by stating several off-topic useless facts about himself. I thought "oh no, here we go again" but was pleasantly surprised how he actually integrated the personal facts in with the main presentation content.
Dennis made an interesting statement that stuck with me (besides the eight principals which I've heard before) starting around 7:15 in the video:
"From that historical analysis we can extract a set principals and guidelines. The principals are what drives the design. The guidelines are simply derivations of the principals for an individual context. Principals are whats important. Principals and data drive successful design."
This is an interesting way to introduce the principals. He leaves it unsaid, but basically the principals are timeless patterns independent of any technology. Guidelines are how you apply them to, e.g. Surface, iPhone, etc.