ActionTrip has published their own two-page preview of Irrational Games' BioShock, after checking out the sci-fi RPG firsthand during this year's E3.
To the best of my knowledge, the idea is to create an open-ended game in the sense that there will be no levels, but more importantly, Irrational is attempting to create the illusion of a living and breathing world. To try and emphasize the emotional bond between the NPCs and the empathy created between the player and other actors in the world. One of the main vessels for this illusion is the architecture of the Artificial Intelligence.
Ken Levine explains: "We built what we call an AI ecology. AIs have goals of their own. First, we have several classes of AI. There are the Aggressors who were the foot soldiers of Rapture during the conflict. They behave pretty much like monsters that you're accustomed to seeing in games. They're very aggressive toward you. But there are also two other classes of AIs in the world called Protectors and Gatherers -- this big guy and this little girl. And the Gatherer's role in the world is to go around collecting this resource, 'Adam,' which is what drives all these genetic changes from bodies left over from the war. They sort of recycle that material and are able to recycle that biologically, in their own body, and they're guarded by these big protectors, these big lugs you see in these diving suit get-ups. And they won't bother you if you don't bother them. They are carrying around a lot of resources around that you might need. So the aggressors are interested in them, and there is often conflict between the Aggressors and them, and you're potentially interested in them. But if you don't bother them, you just observe them going through their behaviors; they have a relationship with each other. They're a team.